Fort Zachary Taylor State Park is the southernmost State Park, occupying 54 acres on the very south-western point of the island. Factually, it is further south than “Southernmost Point”.
The Fort began construction in 1845 and was completed in 1866, and currently is the largest cache of Civil War armaments in the world. Walking amongst the empty corridors feels like a step back through time. I particularly liked exploring some of the barracks, holding cells, and closely examining the cannons.
There is a nominal entry fee, but the State Park is a wonderful way to spend the afternoon. Exploring the Fort can easily occupy an hour, and afterwards there is a beautiful beach to relax on.