Bob Rodale Cycling & Fitness Park

Upper Macungie Township, PA

In the rolling limestone country of the Lehigh Valley, a new American building material was born. In 1871 David O. Saylor began producing portland cement at Coplay, and by November 1889 the region pioneered the commercial use of the rotary kiln — a continuous-process furnace that turned cement-making from a slow batch craft into true industrial mass production. The valley's rich cement rock and rail links let the industry take root and dominate, supplying the mortar and concrete of a rapidly modernizing nation.

Philadelphia, PA

This towering steel barrel once formed the center gun of Turret 1 aboard the USS New Jersey, an Iowa-class battleship that stands today as a museum ship on the Camden waterfront across from Philadelphia. Each of these 16-inch guns could hurl a shell weighing as much as a small car more than 20 miles, and this one spoke in two very different wars — bombarding enemy positions in the Pacific during World War II, then again off the Korean coast a decade later. A single artifact like this collapses the distance between the factory floor of American industrial power and the far shores where that power was felt.

Scranton, PA

In the mid-19th century, northeastern Pennsylvania's anthracite fields ran on ingenious gravity railroads — lines that let loaded coal cars coast downhill by their own weight, with stationary steam engines hauling the empties back up a chain of inclined planes. The Pennsylvania Coal Company's route carried anthracite between the mines around Pittston and the canal at Hawley for more than three decades. This surviving 'Pioneer' car, retired when the gravity line gave way to conventional steam locomotives, was handed over to the City of Scranton in 1909 as a relic of that vanished technology.

Londonderry Township, PA

On March 28, 1979, a combination of equipment failures and confused human response sent the Unit 2 reactor at Three Mile Island into a partial core meltdown, the most serious accident in the history of American commercial nuclear power. As operators struggled to understand what their instruments were telling them, a small amount of radiation escaped and tens of thousands of nearby residents fled their homes amid days of uncertainty. Though the containment building largely held and no clear public health catastrophe followed, the frightening near-disaster on this island in the Susquehanna River became a defining moment in the nation's relationship with atomic energy.