Maple Leaf, Civil War archaeological site in Duval County, United States.

Maple Leaf is a side paddlewheel steamship launched in 1851 at the Marine Railway Yard in Kingston, Upper Canada, measuring 181 feet long and 24.7 feet at the beam. It lies in the St. Johns River west of the Mandarin neighborhood in southeastern Duval County, Florida. The U.S. Army Corps of Engineers removed all structures above the main deck in the 1880s to clear the channel, leaving the hull intact below that line.

Maple Leaf was built in 1851 at the Marine Railway Yard in Kingston, Upper Canada, as a side-paddlewheel freight and passenger steamer 181 feet long with a 24.7-foot beam. Chartered by the Union Army in the Civil War, it struck a Confederate torpedo, a moored mine, while crossing the St. Johns River near Jacksonville on April 1, 1864. Four crew members died, the war's first mine casualty; USS Norwich inspected the wreck the next day and Captain Henry W. Dale judged ship and cargo a total loss.

The Maple Leaf's cargo included personal belongings of Union soldiers, and the river mud kept them intact. The site lies west of the Mandarin neighbourhood, and its Smithsonian trinomial is 8DU8032. A National Historic Landmark plaque stands at 30° 19.461′ N, 81° 39.683′ W.

The wreck lies in the St. Johns River west of the Mandarin neighborhood, in southeastern Duval County; its National Historic Landmark plaque is at 30° 19.461′ N, 81° 39.683′ W. The site is an underwater archaeological location, so it is reached by boat and seen only by diving, and any research or excavation needs permits.

The vessel carried around 400 pounds of military and personal items from three regiments, remarkably preserved in the river's anaerobic mud conditions. This exceptional preservation allows archaeologists to gain detailed insights into the material culture of the era.