Historic Markers in Pennsylvania

Cornwall, PA · est. 1948

Peter Grubb raised this charcoal-fired iron furnace in 1742, tapping the rich ore of the Cornwall hills to smelt pig iron in an age when American industry was still in its infancy. Under later owners—most famously the Coleman family—the works ran for more than 140 years, outlasting nearly every one of its colonial-era rivals. Preserved as a state historic site, it survives as the best intact example of an early Pennsylvania ironmaking plantation.

Cornwall, PA · est. 1948

Built by ironmaster Peter Grubb in 1742, this charcoal furnace drew on the abundant iron ore of the Cornwall hills and stayed in blast until 1883—an extraordinary run of nearly a century and a half. It smelted iron through the colonial era, the Revolution, and deep into the industrial age before finally falling cold. Today the Pennsylvania Historical and Museum Commission cares for the site as a monument to the state's ironmaking heritage.

West Cornwall Township, PA · est. 2005

Founded in 1742 by Peter Grubb beside a rich vein of iron ore and vast charcoal-making forests, Cornwall Iron Furnace grew into a self-sufficient industrial village complete with an ironmaster's mansion and workers' homes. Its furnaces poured pig iron, cast goods, and cannon for the Revolutionary War before passing to Robert Coleman in 1798 and running until 1883. Remarkably, the works survive fully intact nearby — a rare window into early American ironmaking.

Wayne Township, PA · est. 2010

Founded in 1876 as the "Western Hatchery," the Corry facility became Pennsylvania's pioneer trout hatchery and the longest continuously operating one in the state. Fed by steady, cool springs ideal for raising fish, it helped seed the Commonwealth's streams during an era when Americans were beginning to conserve and manage wild resources. Its work fueled a growing outdoor-recreation economy and jobs tied to the state's rising reputation for sport fishing.

Selinsgrove, PA · est. 1966

Jacob Coxey was born in this Snyder County town in 1854 and grew into a reform-minded businessman with a bold idea. In 1894, amid a crushing economic depression, he led a march of jobless men—"Coxey's Army"—from the Midwest to Washington, demanding that the government create jobs through public works. Though he was arrested for walking on the Capitol lawn, his protest thrust the plight of the unemployed into the national spotlight.

Catasauqua, PA · est. 1997

On the Fourth of July, 1840, Welsh ironmaster David Thomas fired up a furnace in Catasauqua that finally proved anthracite coal could smelt iron on a commercial scale. Earlier attempts had failed, but Thomas's hot-blast furnace for the Lehigh Crane Iron Company soon turned out 50 to 60 tons of pig iron a week, and the works grew to six furnaces before closing in 1930. The success helped shift American iron production away from charcoal and toward the hard coal of Pennsylvania's mountains.

Meadville, PA · est. 1982

Formed from Allegheny County in 1800 and named for Colonel William Crawford, Crawford County grew up around Meadville, which in 1788 became the first permanent settlement in northwestern Pennsylvania. The county proved a seedbed of American firsts: the nation's first direct primary election was held here in 1842, and it became a cradle of both the oil industry and the modern zipper. Meadville anchored settlement in a corner of the state that was still wild frontier when the town was founded.

Pittsburgh, PA · est. 2001

Opened in 1943 in Pittsburgh's Hill District, the Crawford Grill #2 became a beating heart of Black social and musical life, where giants like Art Blakey, Mary Lou Williams, and John Coltrane played to a racially mixed and international crowd. First owned by William 'Gus' Greenlee and later by Joseph Robinson, it was the second of three clubs bearing the Crawford name. In an era of segregation, its stage and dance floor drew people across the color line.

Corry, PA · est. 2008

By 1890, the forests and game of western Pennsylvania were reeling from decades of unchecked logging, development, and hunting. In Corry, businessman H.A. Penrose gathered like-minded men to found the Pennsylvania State Sportsmen's Association, an early voice for wildlife conservation and the enforcement of game laws. Their advocacy bore fruit in 1895, when the state legislature created the Board of Game Commissioners — the seed of today's Pennsylvania Game Commission.

Lower Windsor Township, PA · est. 1960

About 1730 the frontiersman Thomas Cresap settled along the Susquehanna on land that Maryland's Lord Baltimore claimed against Pennsylvania, making his fortified home a flashpoint in the bitter boundary dispute between the two colonies. In 1736 Penn's agents forcibly evicted him and burned his "fort," and Cresap moved west into Maryland, where he remained a restless figure in frontier affairs until his death around 1790. His stand gave the border quarrel one of its most colorful episodes.

Cresson Township, PA · est. 2014

In the early twentieth century tuberculosis was a leading killer, and Pennsylvania fought back with a network of state sanatoria where fresh air, rest, and good food were the main treatments. Opened in 1913 on mountain land donated by Andrew Carnegie and guided by health commissioner S. G. Dixon, Cresson became a national model. It was notable for being racially integrated and for running its own nursing school and elementary school, treating some 40,000 patients before it closed in 1964.

Forkston Township, PA

These lakes in the wooded hills of Forkston Township carry the name of J. Q. Reveling, a Pennsylvania figure remembered as the "Dean of Pennsylvania Sportsmen" and a driving force behind the state's early game and fish laws. In the late 19th and early 20th centuries, unregulated hunting and fishing had badly depleted America's wildlife, and reformers across the country pushed to codify seasons, limits, and protections. Naming a body of water for the man credited as "Father of Game and Fish Codes" reflects the era's growing conviction that woods and waters were a public trust worth safeguarding for future generations.

Hatboro, PA · est. 1965

Named for a tavern that once stood nearby, Crooked Billet was the scene of a sharp Revolutionary War clash in the spring of 1778, while the British held Philadelphia. General John Lacey's militia, tasked with choking off supplies flowing to the occupied city, camped here on May 1 when British troops surprised them at dawn, scattering the Americans with heavy losses.

Cross Creek Township, PA · est. 1950

On the eve of the Revolution, Scotch-Irish Presbyterians pushing into western Pennsylvania first gathered for worship in 1775 at the shelter of Vance's Fort, a mile north. By 1779 they had raised their own church nearby and called their first pastor, planting a durable religious community on a still-contested frontier; the stone building standing today was erected in 1864. It is a portrait of how faith and settlement advanced together across the Alleghenies.

Bethlehem, PA

In 1745, just four years after Moravian settlers founded Bethlehem on the banks of the Lehigh River, this two-story log building opened as the community's first public house. Standing beside the ferry landing on the main road into the young settlement, the Crown Inn became a natural stopping place for travelers, and over the decades it welcomed prominent political and military figures passing through eastern Pennsylvania. When a bridge finally supplanted the old ferry in 1794 the inn's fortunes faded; it closed its doors and was torn down in 1857.

Philadelphia, PA · est. 1991

Crystal Bird Fauset lived here when, in 1938, she won a seat in the Pennsylvania House of Representatives and became the first Black woman elected to any state legislature in the United States. A gifted organizer and speaker, she later advised President Franklin D. Roosevelt on race relations within the wartime Office of Civilian Defense. Her career opened doors in electoral politics that had long been barred to Black women.

Straban Township, PA

This monument marks the Confederate Chesapeake Maryland Artillery — Brown's Battery — of Latimer's Battalion in Johnson's Division of Ewell's Corps, Army of Northern Virginia, armed with four 10-pounder Parrott rifles. Marylanders who cast their lot with the South served in units like this one, which fought on the Confederate left during the battle of early July 1863. Gettysburg drew soldiers from across a divided nation, including border-state men fighting far from a home that had stayed in the Union.

Cumberland Township, PA

On the afternoon of July 2, 1863, Brigadier General Joseph B. Kershaw led his South Carolina brigade of McLaws' Division across the Emmitsburg Road toward the Union line near the Rose Farm. The assault carried into some of the fiercest fighting of the second day, on ground remembered for the Peach Orchard and the Wheatfield. This marker fixes the brigade's line of advance.

Archbald, PA

In the anthracite country of northeastern Pennsylvania, 'culm' was the dark waste left over from mining and breaking hard coal — mountainous banks of it once loomed over towns like Archbald. This marker stands on such a heap of anthracite refuse, now slowly greening over as trees reclaim the old industrial scar. Its wry note, 'a raised forest, for now,' captures a landscape still shaped by the coal that built the region.

Carlisle, PA · est. 1982

Carved from Lancaster County in 1750, Cumberland County once stretched all the way to Pennsylvania's western frontier, a vast gateway for settlers pushing toward the Alleghenies. Its seat, Carlisle, was founded the following year and became a crucial staging point on the roads leading west. In the colonial and early national decades, this was the edge of English America, where the Great Wagon Road funneled families toward the interior.

Camp Hill, PA · est. 1948

In the autumn of 1775, as the newly rebellious colonies gambled on carrying the war north, Capt. William Hendricks raised a company of frontier riflemen from the Cumberland County countryside and marched them toward Canada. They joined the desperate assault on Quebec on the last day of the year, fighting under Gen. Richard Montgomery in a driving snowstorm. The attack failed, Montgomery was killed, and Hendricks fell with him.

Mechanicsburg, PA · est. 1992

Incorporated in 1831 and pushing rails from Lemoyne to Chambersburg by 1837, the Cumberland Valley Railroad became the economic spine of a fertile agricultural region. For more than eight decades it carried the Valley's produce and passengers, eventually reaching from Harrisburg toward Virginia before merging into the mighty Pennsylvania Railroad in 1919. The passenger station and stationmaster's house here date to the 1860s.

Pike Township, PA

This bronze plaque marks the Curwensville Dam, a flood-control project the U.S. Army Corps of Engineers built across the West Branch of the Susquehanna River between 1962 and 1965. It rose during the postwar era when the Corps was reshaping American waterways with earthen dams and reservoirs to tame the seasonal floods that had long battered Pennsylvania's river towns. The plaque records the officers who oversaw the work, from the Baltimore District's division and district engineers down to the resident engineer on site.

Damascus Township, PA · est. 1947

In 1755, settlers from Connecticut led by Moses Thomas and Daniel Skinner planted the first colony on the upper Delaware, on lands the Native peoples called Cushetunk. Their arrival reflected Connecticut's sweeping and contested claims to lands stretching west across Pennsylvania. During the Revolution the little settlement was overrun — seized in 1778 by a force of Indians and Loyalist Tories — a casualty of the brutal frontier warfare that swept the Delaware and Susquehanna valleys.

Sugar Grove Township, PA · est. 2019

From her home in the hills of Warren County, Cynthia Catlin Miller turned a family tradition of abolitionism into organized action, founding the Female Assisting Society and the Ladies' Fugitive Aid Society. The Miller Mansion sheltered freedom seekers on the Underground Railroad, and her groups supplied them with food and clothing. In 1854 she and her son Franklin hosted Frederick Douglass and other abolitionists at the Sugar Grove Convention.

Philadelphia, PA · est. 1992

Born in 1732 of White, Black, and Native American ancestry, Cyrus Bustill bought his own freedom and baked bread for Revolutionary War troops during the struggle for American independence. He became a founder of the Free African Society, one of the earliest Black mutual-aid organizations in the nation, and later opened a school for Black children near this site. His life spanned enslavement, revolution, and the first stirrings of organized Black community building in Philadelphia.

Cheltenham Township, PA · est. 2005

Drawn to Philadelphia by the 1876 Centennial, Cyrus H. K. Curtis stayed and built a publishing empire, the Curtis Publishing Company, whose Saturday Evening Post and Ladies' Home Journal reached millions of American households. From 1891 until his death in 1933 he lived nearby at Lyndon, an estate whose Frederick Law Olmsted-designed grounds now form the public Curtis Arboretum. Only Curtis Hall, the home's music room, still stands.

Leechburg, PA

From 1829 to 1853, D. Leech & Company—later the Western Transportation Company—ran an integrated freight and passenger network along the Pennsylvania Mainline Canal, stitching together canalboats, wagons, railroads, and steamships into one of the state's most extensive forwarding businesses. With agents in at least ten states, it moved goods between major cities and even partnered with the Pennsylvania Railroad, building new rail lines for them. Its boatbuilding yard stood near here.

Leet Township, PA · est. 2018

Opened in 1917 in the former Watson family home, this institution began as a residential school for children with disabilities. In 1952 it became the stage for one of medicine's great turning points: Dr. Jonas Salk, aided by medical director Dr. Jessie Wright, carried out the first human trials of his polio vaccine here, working with patients, staff, and neighborhood children. The success of those tests led to the vaccine's 1955 approval and the eventual near-eradication of a disease that had terrified a generation of American families.

Pittsburgh, PA · est. 1983

Daisy Lampkin was one of the most formidable organizers of the twentieth-century Black freedom struggle, working from this Pittsburgh home. As the NAACP's National Field Secretary from 1935 to 1947, she was a fundraising and membership powerhouse who helped build the association into a mass movement, while also leading the Lucy Stone Civic League and helping charter the National Council of Negro Women. She was equally a force in Black journalism as a vice president of the influential Pittsburgh Courier.

Tionesta, PA · est. 1947

Along the Allegheny River in what is now Forest County stood one of a cluster of Native refuge towns visited by the Moravian missionary David Zeisberger in the 1760s. Known by the Munsee word for "muskrat," the town was later called Damascus, and at the time it was home to a Seneca sentinel chief who watched over this stretch of the river. The site belongs to a fraught moment when displaced Delaware, Munsee, and other Native peoples gathered in the upper Ohio country amid the pressures of colonial expansion and missionary activity.

Gettysburg, PA · est. 1991

Born free in Charleston at a time when education for Black Americans was often outlawed, Daniel Alexander Payne became one of the 19th century's most influential Black religious leaders. While studying at Gettysburg's Lutheran Seminary in 1837 he also taught here at the college, and he went on to be elected a bishop of the African Methodist Episcopal Church in 1852 and to lead Wilberforce University, one of the first colleges owned and run by African Americans.

Exeter Township, PA · est. 1947

Daniel Boone was born here in the Oley Valley on November 2, 1734, to a Quaker family, and spent his first sixteen years in the Pennsylvania backcountry before the family moved south. The hunting, tracking, and woodcraft he learned on this ground carried him into legend as the pathfinder of Kentucky's Wilderness Road. The homestead a few miles north is preserved as a historic site.

Exeter Township, PA · est. 1957

Daniel Boone, born here in the Oley Valley in 1734, spent his first sixteen years on the family homestead before the Boones pushed south and west into the Carolina and Kentucky backcountry. Long before he became the legendary blazer of the Wilderness Road and a symbol of American frontier daring, he was a Pennsylvania farm boy hunting the woods of Berks County. The homestead a few miles north is preserved today as a state historic site.

Amity Township, PA · est. 1957

This plaque honors Daniel Boone (1734-1820), the famed pioneer and scout who was born just a few miles away in the Oley Valley and spent his earliest years there. The area's rolling Berks County farmland was Boone's first world before the family migrated south, launching the life of wandering and trailblazing that made him a household name. The nearby birthplace survives as a state historic shrine.

Exeter Township, PA · est. 1948

On the rolling farmland of Berks County stood the log dwelling where Daniel Boone was born in 1734 to a Quaker family of English and Welsh descent. Boone spent his first sixteen years here, learning to hunt and range the Pennsylvania woods before the family pushed south and west, skills that would carry him into legend on the trans-Appalachian frontier. The homestead endured long after the Boones departed and is preserved today by the Pennsylvania Historical and Museum Commission.

East Stroudsburg, PA · est. 1947

Around 1738, Daniel Brodhead pushed into the upper Delaware frontier and planted the settlement first known as Dansbury, the seed of today's East Stroudsburg. He lived here through the uneasy years before the French and Indian War drove many settlers out. His son of the same name would go on to serve as a Revolutionary War commander and later as Pennsylvania's Surveyor General.

Lower Allen Township, PA · est. 1965

Daniel Drawbaugh, born in this village in 1827, was a self-taught mechanic who claimed to have devised a working telephone and sought a patent in 1880. Bell Telephone contested his claims, and in 1888 the courts decided in Bell's favor, leaving Drawbaugh a fascinating footnote in the contested history of the telephone. He worked on his inventions here until moving to nearby Camp Hill in 1904, where he died in 1911.

Lamar Township, PA · est. 1950

Daniel H. Hastings was born in 1849 on a farm a few miles from here and rose to become governor of Pennsylvania from 1895 to 1899. During his single term, the state created its Department of Agriculture and set in motion the plans for the grand State Capitol that stands in Harrisburg today. Though he made his home in Bellefonte for most of his life, his career carried him to the height of Gilded Age state politics.

Hollidaysburg, PA · est. 1989

Daniel Hale Williams spent his boyhood in Hollidaysburg before rising to the front rank of American medicine. In 1891 he founded Provident Hospital in Chicago—one of the nation's first interracial hospitals and a training ground for Black nurses and doctors barred from white institutions. Two years later he performed one of the earliest successful operations on the human heart, and he went on to lead Freedmen's Hospital in Washington and help charter the American College of Surgeons.

Wilkes-Barre, PA · est. 2010

Daniel J. Flood represented northeastern Pennsylvania's coal country in Congress for much of the mid-20th century, rising to power on the House Appropriations Committee. A flamboyant former actor with a waxed mustache, he used his mastery of the legislative process to steer landmark programs — Medicare, Appalachian economic aid, and coal mine health and safety law — while championing Cold War military strength. His long career ended in scandal and resignation.

South Middleton Township, PA · est. 2002

For more than a decade beginning in 1835, Daniel Kaufman risked ruin to help enslaved people fleeing north through Cumberland County. His barn and the dense woods nearby sheltered fugitives to whom he gave food and transport. In 1852 a Maryland slaveholder won a widely watched lawsuit against him, and Kaufman was fined the enormous sum of $4,000 for his defiance of the Fugitive Slave Law. He also founded the village of Boiling Springs.

Millersburg, PA

Millersburg was laid out along the Susquehanna in 1807 by Daniel Miller, and this fountain, marked "Centennial 1857," commemorates a milestone in the young river town's growth. Public fountains like this one were both civic ornaments and practical gathering places on a nineteenth-century main street, offering water to residents, travelers, and horses alike. It stands today as a memorial to the community's namesake founder and its early days.

Stroudsburg, PA · est. 1947

About 1744, frontier founder Daniel Brodhead raised a building here for Moravian missionaries, part of the remarkable Moravian effort to carry their faith to settlers and Native peoples along the Pennsylvania frontier. The mission stood barely a decade: in 1755, as the French and Indian War set the backcountry aflame, it was destroyed in the raiding that emptied the region. Its site lay beside what is now the cemetery.

Sunbury, PA · est. 1947

In the 1830s, hauling anthracite out of Pennsylvania's coal country meant improvising, and this early line did exactly that—opening in 1835 with cars rolling on wooden rails behind horses before a steam locomotive arrived in 1838 and iron rails in 1853. Its terminal near Sunbury was a transfer point where coal was loaded onto canal boats bound for Philadelphia and Baltimore, stitching the interior mines to distant markets.

Darby, PA · est. 1952

Set aside in 1682 as William Penn's Quaker colony was taking root, the Darby Friends Burial Ground has received the dead of this community without interruption for well over three centuries. The land was donated by John Blunston, an English Quaker who founded Darby and rests here himself. The grounds also hold the grave of John Bartram, the largely self-taught colonial botanist whose plant collecting and famous garden near Philadelphia earned him fame on both sides of the Atlantic.

Rostraver Township, PA · est. 1994

On December 19, 1907, an explosion tore through the Darr coal mine near Van Meter, killing 239 men and boys — many of them Hungarian immigrants who had come to America for the promise of steady work underground. It was the deadliest blow in the deadliest month American coal mining has ever known: more than 3,000 miners died that December, including 34 in the nearby Naomi mine weeks earlier. In Olive Branch Cemetery, 71 Darr miners lie together, 49 of them never identified.

Harrisburg, PA · est. 1982

Established in 1785 from Lancaster County, Dauphin County took its name from the eldest son of France's King Louis XVI, a nod to the French alliance that had helped win American independence. Its seat, Harrisburg, was laid out that same year at a strategic crossing of the Susquehanna River. In 1812 Harrisburg became Pennsylvania's capital, and it was chartered a city in 1860, growing into the seat of state government.

Lower Mount Bethel Township, PA · est. 1947

In 1744, the young Presbyterian missionary David Brainerd lived in a log house in this corner of the Forks of the Delaware, laboring to bring Christianity to the region's Native peoples. Racked by the illness that would kill him at 29, Brainerd poured his hopes and torments into a diary that, published after his death by Jonathan Edwards, became one of the most widely read spiritual journals in American history. His brief, feverish ministry left a mark on frontier Pennsylvania far larger than his short life would suggest.

Philadelphia, PA · est. 1991

David Bustill Bowser, a self-taught Black artist, lived and worked here in 19th-century Philadelphia. He began painting signs, banners, and emblems—the everyday commercial art of the era—before turning to portraiture. Among his subjects were Abraham Lincoln, whom he painted several times, and the abolitionist John Brown, linking his brush to the great antislavery cause of his age.

Pittsburgh, PA · est. 1985

Born in Pittsburgh in 1889, David L. Lawrence rose through the city's Democratic politics to become mayor and then Pennsylvania's governor from 1959 to 1963. He is best remembered for the postwar "Pittsburgh Renaissance," a sweeping effort to clear smoke, curb flooding, and rebuild the city's core. His push to redevelop the Golden Triangle helped turn the point where the rivers meet into Point State Park.

Leechburg, PA

In the 1820s Pennsylvania set out to bind its interior together with a state-built network of canals, and men like David Leech turned that ambition into ditches, locks, and towns. A Bucks County native and Allegheny College–trained engineer, Leech came to the Kiskiminetas valley in 1827 to build a lock and dam for the Pennsylvania Canal, then platted a town beside his work in 1829 and gave it his name. Leechburg grew up as a canal town, its fortunes tied to the boats, freight, and travelers moving along the waterway that Leech helped construct.

Easton, PA · est. 1953

At "The Forks" where the Lehigh meets the Delaware, David Martin secured grants in 1739 and 1741 to run a ferry across the water — one of the vital crossings that stitched frontier Pennsylvania to the routes heading west. For decades travelers, wagons, and goods depended on it, and during the Revolutionary War it carried troops and supplies for the American cause. It served until 1806, when bridges and better roads finally overtook the old ferry.

Huntingdon, PA · est. 1955

David R. Porter made his home in this house while building a career that carried him from the iron furnaces of central Pennsylvania to the governor's chair, which he held from 1839 to 1845. Affectionately called "our own Davy R.," he embodied the era when ironmasters were both industrialists and political leaders. His son Horace, born here in 1837, went on to distinction as a soldier and diplomat.

Mount Pleasant Township, PA · est. 1950

In the 1780s the rolling country of Washington County was disputed ground, and David Reed led a band of Covenanter squatters who had settled on land the tract belonged to none other than George Washington. On September 20, 1784, thirteen of these Scotch-Irish pioneers gathered at Reed's log home to face Washington himself and refuse his demand that they leave. Their defiance captures the raw friction between eastern land titles and the settlers who had already cleared and worked the ground.

Philadelphia, PA

David Rittenhouse (1732–1796) was one of early America's foremost men of science — an astronomer, clockmaker, and instrument builder who won fame for observing the 1769 transit of Venus and later served as the first director of the United States Mint. This sundial marks the site of his birth and honors his mastery of astronomy and horology, the precise measurement of time. A self-taught Pennsylvanian, he embodied the Enlightenment ideal of the patriot-scientist.

Philadelphia, PA · est. 2004

David Salisbury Franks was among the small number of Jewish officers to serve the American cause during the Revolution, rising to major and serving as aide-de-camp to General Benedict Arnold. When Arnold's treason was exposed, suspicion inevitably fell on the men closest to him, and Franks endured investigation before being formally cleared and going on to diplomatic service. He died in Philadelphia's 1793 yellow fever epidemic and, having no coreligionists to bury him, was laid to rest at Christ Church by a Christian neighbor.

Bethlehem, PA · est. 2006

Born in Germany in 1728, David Tannenberg emigrated in 1749 to the Moravian religious community at Bethlehem, part of the wave of German-speaking settlers who shaped colonial Pennsylvania. Trained under organ builder Johann Gottlob Klemm at nearby Burnside Plantation, he went on to craft nearly fifty pipe organs prized for their tonal richness and beauty. He was still at work when he died in York in 1804.

Catasauqua, PA · est. 2001

David Thomas carried a hard-won secret across the Atlantic from Wales: how to smelt iron using abundant, slow-burning anthracite coal rather than scarce charcoal. Settling in the Lehigh Valley, he built the Crane Iron Works, widely credited as the first anthracite iron furnace to succeed both technically and as a business. His breakthrough transformed eastern Pennsylvania's hard-coal region into an industrial powerhouse and earned him the title "father of the American anthracite iron industry."

Bethany, PA · est. 1947

In this house in Bethany, David Wilmot was born on January 20, 1814. A Pennsylvania congressman, he gave his name to the Wilmot Proviso of 1846, a proposal to bar slavery from any territory won in the Mexican War. Though it never became law, the Proviso set off one of the fiercest debates in American politics, hardening the sectional divide over slavery's westward spread in the years before the Civil War.