The Camp Jackson incident, which occurred in St. Louis on May 10, 1861, was the first significant event to occur in the Civil War after Fort Sumter. It was the first time units of opposing infantry confronted each other.

An incredible congregation of the famous and soon-to-be-famous witnessed the events of May 10. Most remarkably, this included 3 of the 4 men who would command the armies of the United States in the post-War period. In 1860-61 John M. Schofield, commanding general of the Army from 1888-1895, was an instructor of physics at Washington University in St. Louis, on leave from the Army, and re-entered the service as chief of staff to federal commander Nathaniel Lyon. He was at Camp Jackson in this role. William Tecumseh Sherman (Commanding General, 1869-1883) had recently accepted an appointment as president of a street railway company, and moved to St. Louis. He and his son Willie were among the spectators at Camp Jackson, and had to “hit the dirt” when the bullets began to fly. In May, 1861, Ulysses S. Grant (Commanding 1864-1869) was on a recruiting mission at Belleville, Illinois, and crossed the river to St. Louis where he visited the U.S. Arsenal and watched as the federal troops marched from there to Camp Jackson. During these 30 years, the other commanding general was Philip Henry Sheridan (1883-1888). On May 10, 1861, Sheridan was a lieutenant in the regular army, posted in Oregon. It was not until December, 1861, that Sheridan was transferred East. His first post in the war zone – St. Louis.