San Antonio–San Diego Mail Line
The San Antonio–San Diego Mail Line, also known as the Jackass Mail, was the earliest overland stagecoach and mail operation from the Eastern United States to California, in operation between 1857 and 1861. It was created, organized and financed by James E. Birch the head of the California Stage Company.
Source: Wikipedia — San Antonio–San Diego Mail Line (CC BY-SA 4.0)