The Battle of St. John's Bluff was fought from October 1–3, 1862, between Union and Confederate forces in Duval County, Florida, during the American Civil War. The battle resulted in a significant Union victory, helping secure their control of the Jacksonville area.
Early in the war, Confederate Brigadier General Joseph Finnegan established an artillery battery on St. John's Bluff near Jacksonville, Florida, to stop the movement of Union Navy ships up the St. Johns River. This was part of a series of Confederate defensive works that had been constructed near Fort Caroline. But once Union forces had occupied the town of Jacksonville, it became necessary for them to also reduce the enemy batteries along the St. Johns River to consolidate control of the general area.
Union Brigadier General John Milton Brannan embarked with about 1,500 infantry aboard the transports Boston, Ben DeFord, Cosmopolitan, and Neptune at Hilton Head, South Carolina, on September 30, 1862. The flotilla arrived at the mouth of the St. John's River on October 1, where Commander Charles Steedman's gunboats— USS Paul Jones, USS Cimarron, USS Uncas, USS Patroon, USS E. B. Hale, and USS Water Witch—joined them.
By midday, the gunboats approached the bluff, while Brannan began landing troops at Mayport Mills. Another Union infantry force landed at Mount Pleasant Creek, about five miles in the rear of the Confederate battery, and began marching overland on October 2. Outmaneuvered, Lieutenant Commander Charles F. Hopkins, the local Confederate commander, abandoned the position after dark. When the gunboats approached the bluff the next day, its guns were silent.