The Battle of Baton Rouge was decided on September 21, 1779 during the American Revolutionary War. Baton Rouge was the second British outpost to fall to Spanish arms during Bernardo de G?lvez' drive into British West Florida.

Moving forward from Fort Bute, G?lvez arrived at Baton Rouge on September 20 and discovered a well-fortified town garrisoned by over 300 regulars. Outflanked by the guns on the fort and unable to advance his own artillery, G?lvez ordered a feint to the north through a forest ringing the town. The British turned and unleashed deadly volleys at this body, but because of the substantial foliage, caused only three casualties. Meanwhile, G?lvez' engineers and siege specialists created a line of trenches and established secure gunpits. G?lvez turned his guns on the fort.

The British endured three hours of vicious shelling and then capitulated. G?lvez' surrender terms included the capitulation of the 80 regular infantry in nearby Fort Panmure, present-day Natchez. This arrangement cleared the Mississippi River estuary entirely of British forces, putting the great waterway firmly under allied control. Within a few days of G?lvez' victory, American privateers slipped into Lake Pontchartrain with his blessing and successfully drove British forces from those waters.