The Mexican War (1846-48) was the first time an American War was fought totally on foreign soil. During this war, more than 73,000 state militia participated in the war with Mexico. These militia forces made up seventy percent of the U.S. Army.
During this conflict that Colonel Jonathan D. Stevenson of the New York National Guard was selected by President James K. Polk to raise a regiment for service in California. Stevenson’s Regiment was mustered into federal service on August 1, 1846 as the Seventh Regiment (later designated the First Regiment New York Volunteers). At the end of the war, many of Stevenson’s Regiment would later join the California National Guard.

The first California Volunteer Militia was organized during this war by Captain John Charles Fremont, U.S. Topographical Engineers. Formed as the California Battalion, this force was organized in May 1946 under the newly formed Bear Flag Republic. Fremont was promoted by Commodore Robert Field Stockton, Commander of U.S. Naval Forces in the Pacific, and given command of all Volunteer Militia on July 23, 1846. Fremont and the California Battalion came into prominence when in January 1847 they accepted the surrender of the Californios, thereby ending the conflict in California. Fremont later became one of California’s military governors and one of this State’s first U.S. Senators.
Following the Mexican war, California’s first National Guard unit was formed on July 27, 1849 under the then military governor, Brig. Gen. Bennett Riley, as the First California Guard Light Artillery.
California's National Guard
Mexican War Years (1846-1848)
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CW2 Mark J. Denger and LTC Roger D. McGrath
California Center for Military History
Stevenson's Regiment
Captain John C. Fremont and the Bear Flag Revolt
First California Guard
History of the National Guard
Mississippi Rifles
Buena Vista, Mexico -- February 23, 1847
Fighting in the open on a dusty mountainside in a foreign land a thousand miles from home, facing an enemy many times its own strength, the Mississippi Rifles, commanded by Colonel Jefferson Davis, displayed a rock-like defense against a Mexican attack in response to the command, "Stand Fast, Mississippians!" Earlier, the battle had reached a critical stage when the Rifles (in the action depicted) were ordered to attack Mexican cavalry and infantry advancing on the Americans. The "hard-fighting Mississippi gentlemen" moved up, fired, then drew Bowie knives and closed in. The Rifles--the 155th Infantry of the modern Mississippi Army National Guard--thus wrote another chapter in the proud National Guard tradition.
Painting by by Ken Riley, National Guard Heritage Series