[2] At the start of the Civil War, Major Ketchum now with US Fourth Infantry Regiment commanded Fort Dalles in Oregon, protecting settlers from Indian raids.
He was ordered to San Francisco and then sent to take command of the federal troops in Southern California to protect it from secessionist rising and Confederate invasion from Arizona or Texas.
Headquartered in San Bernardino, California, his troops kept an eye on the secessionists of the region and reinforced Fort Yuma.
Relieved by California Volunteer troops, Ketchum and his regiment assembled in San Pedro for the voyage to eastern United States in the late fall of 1861.
He died on June 28, 1871, in Baltimore, Maryland, under suspicious circumstances, the landlady of his boarding house, Ellen G. Wharton being suspected of poisoning him.