In 1751, surveyors Andrew Lewis and his father found a large spring at the present site of Lewisburg, which they named Lewis Spring. The spring attracted settlers, and cabins were built nearby. The early settlers were dispersed during the French and Indian War, with the area once again populated by the late 1760s. In 1774, Camp Union was located there as the rendezvous for Lewis's troops. Fort Savannah was built there by the mid-1770s. William Richmond stated that his regiment wintered at the "Savannah Fort" between October 1775 and the spring of 1776.

Fort Savannah was a large militia fort. Though fortified by the time of the Revolutionary War, there is no evidence of British attacks on Fort Savannah. However, Indians raided in the area, with many battles reported. In 1778, a company under Samuel Lewis left Fort Savannah to assist nearby Fort Donnally, which was under attack by Indians, and drove them from the area. Later, in 1790, it was reported that "Mad Anne" Bailey made a heroic 100-mile dash from the besieged Fort Lee at present Charleston to "Fort Union in Lewisburg" to obtain gunpowder.

In 1782, a 40-acre tract was decreed by the Virginia Assembly to create the town of Lewisburg near the site of the fort, which (along with Lewis Spring) was set aside as public land.