California's involvement in the American Civil War included sending gold east to support the war effort, recruiting volunteer combat units to replace regular U.S. Army units sent east, in the area west of the Rocky Mountains, maintaining and building numerous camps and fortifications, suppressing secessionist activity (many of these secessionists went east to fight for the Confederacy) and securing the New Mexico Territory against the Confederacy. The State of California did not send its units east, but many citizens traveled east and joined the Union Army there, some of whom became famous.