The regiment can trace its history back to the 7th Infantry Regiment (California). In 1917, the 7th Infantry Regiment (California) consolidated with elements of the 2nd Infantry Regiment (California) to form the 160th Infantry Regiment. On 1 April 1929, the 2nd Battalion of the 160th was reorganized to form the 2nd Battalion of the 185th Infantry Regiment. In March and April 1930, the 2nd Battalion of the 185th expanded to become the 2nd and 3rd Battalions of the 185th. During World War II, the 185th fought in the New Britain campaign and in the Philippines Campaign. Postwar, it was decided the California could support a second National Guard division, the 49th Infantry Division, composed of the 159th, 184th and 185th Infantry Regiments. The 40th Infantry Division was composed of the 160th, 223rd and 224th Infantry Regiments. The 223rd Infantry was formed from the 2nd Battalion of the 185th Infantry Regiment. The 224th Infantry Regiment was formed on 15 October 1946 in Ontario, California from the 185th Infantry Regiment's 3rd Battalion.