Older than the state itself, the first militia company to become an official part of the California National Guard was a militia company known as the First California Guard Light Artillery. Formed by the then military governor of California, Brig. Gen. Bennett Riley, the First California Guard was formed as an artillery company, but also drilled in the tactics of the infantry. At its formation, it consisted of only 41 members but had increased to 100 men by September of that year. By 1890, the First California Guard would become known as Company A, First Regiment of Light Battery, California National Guard.
California's 1849 Constitution provided for both an "army and navy of this State" and the state's first enactment of military law by the Legislature came in 1850, providing for the organization of the State’s militia and the election of an Adjutant General, defining his duties. The state's militia force, under this early enactment, was partitioned into four divisions under four major-generals, with two brigades to a division, and a brigadier-general assigned to each, as well as a quartermaster general. The governor was the commander-in-chief, who could appoint two aides-de-camp with the rank of colonels of cavalry; but the legislature elected the major and brigadier-generals, one adjutant and one quartermaster general, with the rank of brigadier-general, all to be commissioned by the governor.
The state's militia law was patterned after the Militia Act of 1792 and the Legislature by the Statues of 1852, made provisions for the full employment of the militia in matters of internal security. Militia companies were formed rapidly and by December 1854, California had within its boundaries, 24 companies and 1,500 men organized, armed, equipped and ready for service. These companies were organized for various reasons, some to protect settlers from hostile Indians, others to preserve law and order, while others appeared to be purely social in nature. No military services were required of them until 1856, when a vigilance committee unlawfully assumed control over the city government of San Francisco, and the militia was ordered to report for duty by the governor of the state. The year before, the Legislature had again reorganized the militia by the Statues of 1855, providing for six divisions and 12 brigades, and requiring military rolls to be kept by each county.
One of these early militia units, the Sacramento Hussars, in flamboyant uniforms with feather adorned fur caps and red and yellow boots, formed a mounted escort for the first Pony Express rider to reach Sacramento on March 3, 1860. As the debate over slavery in the territories threatened to ignite into a war, the Pony Express, operated by the Central Overland stagecoach line, covered 1,900 miles between Missouri and California; being Washington's only line of contact with the West. In fact, it was the Pony Express that delivered Abraham Lincoln's inaugural address to Californians less than eight days after it was given in March 1861. By October of that year, the telegraph line was completed to California and the Pony Express faded out of existence.
Of the several California militia companies which organized between 1849 and 1861, had within their ranks men who were veterans of the Mexican War, many of whom had served in either the California Battalion, Mormon Battalion or First Regiment New York Volunteers, having both military training and experience. These organized and regulated militia units were caparisoned in regular military fashion.