The Los Angeles Mounted Rifles were formed as a part of a call by California Governor John G Downey for militia companies at the beginning of the Civil War. Enrollment filled quickly in the Mounted Rifles and an organizational meeting was held with 85 men at the Los Angeles County Courthouse March 17th 1861. The name of the company the Los Angeles Mounted Rifles was chosen, and the company mustered into service under Captain Alonzo Ridley and First Lieutenant Joseph Cattick. The rolls showed 8 officers and 64 privates. From the Rifles inception they were known as pro-Confederacy.
Once the news reached the west coast that Fort Sumter had fallen, Ridley decided to take Rifles to Texas. They were joined by former United States Officers Albert Sidney Johnston and Lewis Addison Armistead, who had resigned their commissions.
After making a long journey across the desert the Rifles were disbanded as a unit the second week of August 1861. Most of the members of the Rifles joined Texas units and served throughout the war. Captain Alonzo Ridley stayed with Albert Sidney Johnston through the Battle of Shiloh.
A web site for more information about this subject is California's Confederate Militia: The Los Angeles Mounted Rifles