The Battle of Saint John's River was a military engagement that took place during the American Civil War on March 3, 1862. It involved Union forces attempting to gain control of the strategic Saint John's River in Florida. The battle was part of a larger campaign to secure the region and disrupt Confederate supply lines. Union naval and land forces faced off against Confederate troops defending the area. Although the Union aimed to establish dominance, the battle ended inconclusively, with both sides suffering casualties. The engagement highlighted the importance of river control in the broader context of the war.