Fort Foster was originally built in December,1836, by Col. William S. Foster, and his 430 men. It took he and his men about three weeks to construct the fort using only hand tools and sweat.
During the Second Seminole War, the purpose of Fort Foster was to defend the bridge crossing the Hillsborough River and act as a resupply point for the soldiers in the field.
The fort was garrisoned on and off from December, 1836, thru April, 1838. From January, 1836, thru March, 1837, the fort was garrisoned predominately by sailors. U.S. Navy Lt. Thomas J. Lieb, fifty sailors and 20 artillery soldiers, were assigned to defend the fort and bridge.
The fort was attacked on several occasions, but the worst was in February, 1836, when the Seminoles attempted to set fire to the bridge. The attempts were thwarted by aggressive musket and cannon fire from the sailors and the artillery men within the fort. Seminole attacks increased to a point that forced Lt. Lieb to send a message to Ft. Brooke, where Tampa is today, for reinforcements. 150 Marines were dispatched to Ft. Foster to assist the sailors. When the Marines arrived, the Seminoles rethought their intentions and the hostilities nearly ceased at the bridge crossing.