Fort Fremont was a military installation on Saint Helena Island, Beaufort County.

The fort and battery is historically significant as an example of late nineteenth and early twentieth century military architecture and as one of two surviving coastal fortifications in the United States intact from the Spanish–American War era.
Construction of Fort Fremont started in 1899.
Congress authorized the construction of additional coastal batteries. Authorization resulted due to the $50 million Harbor Fortification Defense Act of 1898. The Spanish–American War was the catalyst for the Harbor Fortification Defense. The Corps of Engineers built Fort Fremont on condemned private property. The Corps hired labor from the Beaufort area to build the military complex.
The fort was the namesake of John C. Fremont.
He was the first presidential candidate of the Republican Party in 1856. Later, Fremont was a Civil War general.
The complex at Fort Fremont consisted of almost 170 acres of land with numerous outbuildings, including an Administration building, guard house, barracks, hospital, stable, mess hall, bakery, commissary, post exchange, lavatory, and water tower. The garrison’s single artillery company operated three 10-inch disappearing guns and two 4.7-inch rapid fire guns. Much of the bastions and the concrete emplacements for the guns remain today.
As early as 1906 the War Department gave serious consideration to its closing, due to budgetary constraints.
A December 7, 1921 Charleston News and Courier article reported that the U.S. Treasury Department requested the site from the U.S. War Department for use as a quarantine station. It was subsequently deactivated as a military installation in 1921.
The War Department decommissioned the Fort and sold at public auction by in 1930.
The Battery is on the National Register of Historic Places (NRHP). Today the fort is a Historical Preserve. Only the 10 inch battery, the rapid-fire battery, and the brick hospital built in 1906 survive. The documentation states that “Fort Fremont is one of only two extant Spanish–American War fortifications which retain their character from that period.”
Source: https://en.wikipedia.org/wiki/Fort_Fremont.