In late August 1779, men of the Opelousas Post Militia left from this place to join other militia units in an attack on British forces in the lower Mississippi Valley. After crossing the Atchafalaya swamp, they joined Brig. General Bernardo de Gálvez, governor of the Spanish province of Louisiana, at Fort San Gabriel a few miles below present-day Baton Rouge. Gálvez's total force included 175 Spanish army veterans, 330 Spanish recruits, 80 free men of color, 160 Choctaws, and about 600 men from various militias along the Mississippi River and from Louisiana's distant posts. On September 22, 1779, Gálvez's effective force of fewer than 900 men laid siege to and captured Ft. New Richmond at Baton Rouge. That victory forced the surrender of Ft. Panmure at Natchez, the British headquarters in the lower Mississippi Valley, and this little-known action, in which the Opelousas Post Militia took part, greatly aided the winning of the American Revolution of 1775-1783.