In 1802, the village was chartered as a town by an Act of the General Assembly. It was laid off into lots and streets on the land of John Carthrea, Jr. and its size was nearly doubled immediately by the "Carthrea addition" of land of John Carthrea, Sr. The growth and prosperity was such that the next year the town of New Haven (now nearly non-existent) was established on the North River bank opposite Port.

In 1784, George Washington, while visiting at the home of Gabriel Jones, had written in his diary about the possible navigability of the South Fork of the Shenandoah to its confluence with the Potomac. In 1814, the New Shenandoah Company was established by Act of the General Assembly (through efforts headed by Stephen Harnsberger) to make the river navigable for flat-bottomed boats. These were called "gundalows," as long as 90 feet. Commodities were brought in from nearby farms, industries, and mines on the eight public roads which led to Port, and were shipped to Harper's Ferry. Boating became a major industry which endured more than a half century.

The Mundy, Smith & Mundy store was built on the site of the first store and post office in Port Republic. During the Civil War, the Lee Tavern stood at the same location. It is now the site of the new Port Republic Post Office.

Many mills were built to take advantage of the water power available in Port Republic, the first of which was built in 1745 before the town was laid out. The Port Republic Mill pictured at right was rebuilt after it was burned in 1864, and it operated until the 1940's. Original mill races are still visible throughout the village of Port Republic. The oldest house still standing was the home of an early tannery owner, John Dundore.