In the early 1900s, the U.S. Bureau of Immigration created a special "Chinese Division" to enforce the Chinese Exclusion Act of 1882, which was the first major U.S. immigration law to ban entry based on race and nationality. Federal agents were sent to Mexican border towns and tasked with secretly photographing, tracking and cataloging Chinese migrants — in a word, to spy on them.

Years before the Border Patrol was formally created in 1924, federal officials began patrolling the U.S.-Mexico border to catch Chinese migrants attempting to enter the country. Immigration officers and "mounted Chinese inspectors" on horseback rode through deserts and borderlands, detaining people based on appearance and perceived foreignness.

These mounted officers, often deputized cowboys or former soldiers,

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