The St. Johns River Lighthouse was built and was the third lighthouse built at the entrance to the St. Johns River. Previous lighthouses were built in 1830 and 1833. The lighthouse is located on what is today the Mayport Naval Air Station. During the Civil War, the river was the scene of intense fighting. In 1864, more than twelve ships were sunk in its waters. One of those ships, the Maple Leaf, was sunk just offshore of Mandarin Point in Jacksonville by a Confederate mine. The luxury steamer was pressed into service as a supply ship and contained supplies for three Union regiments. The Maple Leaf was discovered in 1984 by an expedition team under 20 feet of water and 7 feet of mud.