Fort De Soto Park Fort De Soto Park is located just outside the city of St . Petersburg , Florida . This park , operated by Pinellas County , is made up from five offshore keys , or islands lying to the city ' s south - southwest : Madelaine Key , St . Jean Key , St . Christopher Key , Bonne Fortune Key and the main island , Mullet Key . Today all are connected by either bridge or causeway to each other . The island group is accessible by toll road from the mainland . . The park is a ' gateway site ' for the Great Florida Birding Trail . History . In 1849 , Brevet Col . Robert E . Lee ( the famous American Civil War commander ) and three other US Army Engineers surveyed the area and recommended Mullet and Egmont Keys become fortified . Both keys could only be reached by boat , since they were islands off the mainland . Union troops were stationed on the two keys during the Civil War ( 1861 – 1865 ) to aid in the Union blockade of Tampa Bay . The keys were again abandoned by the military until 1882 when military reservations were officially created on the two keys . However , it would be several years before actual permanent construction would commence as a result of defense considerations linked to the Spanish - American War . Hillsborough County established a quarantine station on the eastern side of Mullet Key in 1889 . It became known as Mullet Key Quarantine Station . The Marine Hospital Service took over jurisdiction of the station in 1901 . The duty of the station was to inspect aliens aboard ships arriving from foreign ports . By 1925 the station operated with fifteen buildings . The quarantine station operated until 1937 , when the Public Health Service transferred its operations there to Gadsden Point , near Tampa . The main operation on Mullet Key , however , became Fort De Soto in 1900 , named for Spanish explorer Hernando de Soto . The Army post was officially a subpost of Fort Dade , which was constructed on Egmont Key . These posts were to contain batteries of artillery and mortars to protect Tampa Bay from any invading forces . Construction of Fort De Soto began in November 1898 and was completed in 1906 . The foundation was constructed of a shell concrete formula and the walls and ceiling used a shell , stone and concrete mix . The main attractions at the completed post were the artillery and mortar batteries , Batteries Laidley and Bigelow . The post consisted of 29 buildings . The post ' s features included a large barracks , a hospital , a guardhouse , a blacksmith and carpenter shop , an administration building , and mess hall with kitchen , a bakery , and a storehouse . The site also had brick roads , concrete sidewalks and a narrow - gauge railroad to aid in moving materials and supplies around the post . The post was active from 1898 to 1910 . At least one company was present at Fort De Soto at all times and many times several units were present . Mosquito es were a constant problem and the post was very hot in the summers . In 1910 most troops were moved to Fort Morgan in Alabama . Only a caretaker force remained . By 1914 only a sergeant and game warden remained at the post . Through most of World War I a larger caretaker force was at the post , usually with about 22 privates , two noncommissioned officer s and two commissioned officer s . In 1917 four of the post ' s mortars were disassembled and shipped to Fort Rosecrans , in San Diego , California . In November 1922 the Army announced it would soon close both Forts De Soto and Dade . On May 25 , 1923 , the forts were officially abandoned and only one caretaker remained at each post . A number of tropical storms and hurricanes severely damaged the buildings on the post . A few were destroyed , as was Battery Bigelow in 1932 . The Army attempted to sell the post , but there was little interest . In September 1938 Pinellas County bought the areas on Mullet Key for $ 12 , 500 . Two years later the War Department decided it wanted Mullet Key back for use as a bombing range by the U . S . Army Air Corps . In June 1941 the key was purchased back from Pinellas County for $ 18 , 404 and turned into a subpost of MacDill Field . In 1948 Pinellas County again purchased the key and it permanently remained county property . In 1962 a toll road , the Pinellas Bayway ( formerly State Road A19A , now SR 682 ) , was completed to the mainland , enabling island visitors to arrive by car . On December 21 , 1962 , Fort De Soto Park opened . On May 11 , 1963 , Fort De Soto Park was officially dedicated . Its facilities have been expanded over the years . The quartermaster storehouse was reconstructed to become the Quartermaster Storehouse Museum . On December 2 , 1977 , the Fort De Soto batteries were placed on the National Register of Historic Places . In 2003 , a portion of the Marvel comic - inspired film " The Punisher " was filmed on Mullet Key and Fort Desoto as a mock - up of Puerto Rico . Early History . The area of Fort Desoto for over 400 years has attracted a variety of visitors . Among the earliest was the Tocobaga Indians who preceded Spanish explorers which begin the westerns world entrance into the area . On April 15 , 1528 , Panfilo de Narvaez landed on the shore of the west coast of Florida between St . Petersburg Beach and Clearwater . This Spanish explorer with a group of conquistadors explored the barrier islands in the area . This area was further explored on May 30 , 1539 , when Hernando De Soto arrived on the shores of Tampa Bay . Recreational activities and amenities . The park is open year - round and has the following features :