The inspectors, usually called 'mounted guards', operated out of. Though they never totaled more than 75, they patrolled as far west as trying to restrict the flow of illegal Chinese immigration. In March 1917, Congress authorized a separate group of mounted guards, often referred to as 'mounted inspectors'. Most rode on horseback, but a few operated automobiles, motorcycles and boats. Although these inspectors had broader arrest authority, they still largely pursued Chinese immigrants trying to avoid the and of 1882. These patrolmen were Immigration Inspectors, assigned to inspection stations, and could not watch the border at all times. Soldiers along the southwest border performed intermittent border patrolling, but this was secondary to 'the more serious work of military training.'
Immigrants encountered illegally in the U.S. By the Army were directed to the immigration inspection stations. Were also sporadically assigned to patrol duties by the state, and their efforts were noted as 'singularly effective'. A Border Patrol Agent practice firing a Thompson submachine gun near El Paso in 1940. Border Patrol was founded on May 28, 1924 (by the ) as an agency of the to prevent along the and the. The first Border Patrol station began operations in Detroit, Michigan in June 1924. A second station in El Paso, Texas began operations in July 1924.