Bagdad-Matamoros, C.S.A.
Brownsville, TX
During the Civil War, Brownsville and the twin towns of Bagdad and Matamoros across the Rio Grande became a vital loophole in the Union blockade. Because Mexico was neutral, Confederate cotton hauled overland from as far as Arkansas could be ferried across the river and shipped to Europe, returning as guns, medicine, cloth, and shoes. This border trade was, as the marker says, the South's lifeblood when its own ports were sealed.