The Mirror Building also called the Butterfield Overland Mail Company Los Angeles Building was a large brick building in Los Angeles built by Butterfield Overland Mail Company built in 1858. The Mirror Building was designated a California Historic Landmark (No.744) on July 5, 1960. The Mirror Building had business offices and housing space for traveling workers. There was a large stable in the back of the buildings for the horses, along with a large workshop to repair the stagecoaches. The first Butterfield Overland Mail stagecoach from St. Louis to arrive was on October 7, 1858. The Butterfield Overland Mail Company was founded by John Butterfield, who later founded American Express.

Butterfield Overland Mail was a stagecoach service in the United States operating from 1858 to 1861. It carried passengers and U.S. Mail from two eastern termini, Memphis, Tennessee, and St. Louis, Missouri, to San Francisco, California. The routes from each eastern terminus met at Fort Smith, Arkansas, and then continued through Indian Territory (Oklahoma), Texas, New Mexico, Arizona, Mexico, and California ending in San Francisco. On March 3, 1857, Congress authorized the U.S. postmaster general, at that time Aaron V. Brown, to contract for delivery of the U.S. mail from St. Louis to San Francisco. Prior to this, U.S. Mail bound for the Far West had been delivered by the San Antonio and San Diego Mail Line since June 1857.