San Augustin Spring, a small but dependable water source in the Organ Mountains east of Las Cruces, gained historical importance during the opening months of the American Civil War. After the Union defeat at the First Battle of Mesilla on July 25, 1861, Major Isaac Lynde abandoned Fort Fillmore and retreated through San Augustin Pass toward Fort Stanton while Confederate forces under Lieutenant Colonel John R. Baylor pursued. Heat, thirst, and lack of water reduced Lynde’s command to about 200 to 300 weakened men by the time it reached the spring. There, on July 27, Baylor overtook the column and forced its unconditional surrender, a humiliating Federal defeat in New Mexico.