Fort De Soto Park, 1,136 acres, is located on five islands at the mouth of Tampa Bay on the Gulf of Mexico. The largest island is Mullet Key, which is where the Quartermaster Storehouse Museum is located. Battery Laidley was the primary defense and Battery Bigelow was the secondary defense for Fort De Soto. Even though Battery Bigelow was destroyed during the hurricane of 1921, the Fort De Soto batteries were placed on the National Register of Historic Places in 1977. Visitors can walk through Battery Laidley, home to the last four surviving carriage-mounted 12-inch seacoast mortars in the continental United States.