Battle of Baton Rouge ( 1779 ) The Battle of Baton Rouge was a brief siege during the American Revolutionary War that was decided on September 21 , 1779 . Baton Rouge was the second British outpost to fall to Spanish arms during Bernardo de Gálvez ' s march into British West Florida . Background . Spain officially entered the American Revolutionary War on May 8 , 1779 , with a formal declaration of war by King Charles III . This declaration was followed by another on July 8 that authorized his colonial subjects to engage in hostilities against the British . When Bernardo de Gálvez , the colonial Governor of Spanish Louisiana received word of this on July 21 , he immediately began to plan offensive operations to take British West Florida . Fort Bute . On August 27 , Gálvez set out by land toward Baton Rouge , leading a force that consisted of 520 regulars , of whom about two - thirds were recent recruits , 60 militiamen , 80 free blacks and mulattoes , and ten American volunteers headed by Oliver Pollock . As they marched upriver , the force grew by another 600 men , including Indians and Acadians . At its peak , the force numbered over 1 , 400 , but this number was reduced due the hardships of the march by several hundred before they reached Fort Bute . At dawn on September 7 , this force attacked Fort Bute , a decaying relic of the French and Indian War that was defended by a token force . After a brief skirmish in which one German was killed , most of the garrison surrendered . The six who escaped capture made their way to Baton Rouge to notify the British troops there of the fort ' s capture . After several days ' rest , Gálvez advanced on Baton Rouge , only from Fort Bute . When Gálvez arrived at Baton Rouge on September 12 , he found a well - fortified town garrisoned by over 400 regular army troops and 150 militia under the overall command of Lieutenant Colonel Alexander Dickson . The troops consisted of British Army regulars from the 16th and 60th Regiments , as well as some artillerymen , and several companies of Germans from the 3rd Waldeck Regiment . British defenses . Dickson had decided weeks earlier that Fort Bute , built in 1766 and in ruins , was not defensible , and had placed most of his troops at Baton Rouge . Beginning in July 1779 , he directed the construction of Fort New Richmond . This fortification was an earthen redoubt with chevaux de frise on the outside . It was surrounded by a moat wide and deep , and fortified with thirteen cannons . Battle . Gálvez first sent a detachment of men further up the river to break communications between Baton Rouge and British sites further upriver . Before the fort he was unable to directly advance his own artillery , so Gálvez ordered a feint to the north through a wooded area , sending a detachment of his poorly trained militia to create disturbances in the forest . The British turned and unleashed massed volleys at this body , but the Spanish forces , shielded by substantial foliage , suffered only three casualties . While this went on , Gálvez dug siege trenches and established secure gunpits within musket range of the fort . He placed his artillery pieces there , opening fire on the fort on September 21 . The British endured three hours of shelling before Dickson offered to surrender . Gálvez demanded and was granted terms that included the capitulation of the 80 regular infantry at Fort Panmure ( modern Natchez , Mississippi ) , a well - fortified position that would have been difficult for Gálvez to take militarily . Dickson surrendered 375 regular troops the next day ; Gálvez had Dickson ' s militia disarmed and sent home . Gálvez then sent a detachment of 50 men to take control of Panmure . He also dismissed his own militia companies , left a sizable garrison at Baton Rouge , and returned to New Orleans with about 50 men . Aftermath . When informed that Dickson had surrendered Fort Panmure , its commander was irate , believing Dickson had surrendered Panmure to get better terms of surrender . Isaac Johnson , a local justice of the peace , wrote that " In the mighty battle between Governor Gálvez and Colonel Dickson , the Spaniards only lost one man and some say not one , the English lost twenty - five and the commanding officer wounded his head on his " tea table " " . The victory at Baton Rouge cleared the Mississippi River estuary entirely of British forces and put the lower reaches of the river firmly under Spanish control . Within a few days of Gálvez ' victory , American and Spanish privateers captured several British supply ships on Lake Pontchartrain , including the remarkable capture of one ship carrying 54 Waldecker troops and ten to twelve sailors by a sloop crewed by 14 native Louisianans . Gálvez was promoted to brigadier general for his successful campaign , and his exploits were immortalized in the poetry of Julien Poydras . He immediately began planning an expedition against Mobile and Pensacola , the remaining British strongholds in West Florida , which would culminate in the capture of Pensacola , the West Florida capital , in 1781 . Baton Rouge remained in Spanish hands for the rest of the war , and Britain ceded both West and East Florida to Spain in the 1783 Treaty of Paris . It would not become American territory until 1810 .