Port Republic is an unincorporated community in Rockingham County, Virginia, United States. The Battle of Port Republic occurred there in the American Civil War.Port Republic was chartered as a town in 1802, at the confluence of the South River and the North River, which join to form the South Fork of the Shenandoah River. This point was the head of navigation on this branch of the Shenandoah, and influenced the town's commercial and strategic importance.By 1832 the town had a population of 160 people. Many mills were built there, the first one in 1745, because of the availability of water power, and the proximity to water transportation to the northern Shenandoah Valley and the Potomac River. The Battle of Port Republic in June 1862 during Stonewall Jackson's Shenandoah Valley Campaign in the American Civil War centered on Port Republic.After the Civil War, Port Republic remained a locus of commerce and industry, with two iron foundries in operation by 1866.