Gold and Revolution
Approximately 20,000 Mexican miners entered California during the Period of rapid migration to California after the discovery of gold from 1848-1855, leading to exponential increases in population and economic growth in the region. However, migration from Mexico was minimal during most of the 1800s.
During the 1870s and 1880s the American West grew economically with the expansion of the railroads, and so did the demand for laborers. During this time, restrictive immigration laws dramatically reduced the numbers of laborers from Asian nations, so U.S. employers began to look to Mexico to fill a rising demand for labor in basic industries including agriculture, mining, construction and transportation.
By 1900, an estimated 100,000 Mexicans had migrated to the U.S. The outbreak of the Mexican Revolution in 1910 caused more movement of people within Mexico and eventually across the border, a trend that continued into the 1930s.