El Paso’s and Texas’s proximity to the border is what made them the first to adopt an anti-Mexican sentiment. But that was going to reach country-wide support in just a few years.
Even though 97% of Mexican landowners decided to become US citizens, as per the 1848 treaty, there was no way to classify them. Some might have been considered “white” like the Irish or German immigrants, but many were not. However, they were not seen as Black or Indian either. There was a variety of subjective terms (some derived from the Spanish caste) that would get used for decades, like “mulatto,” “mixed,” “brown,” or “other.”
In places like El Paso with more exposure to Mexicans, “white” would get used more frequently over time. But there was no set criteria, locally or otherwise. Regardless of the racial terms, in 1868 the 14th Amendment was adopted, and granted birthright citizenship to any “person born in the United States.” Unfortunately, to many in the country, speaking Spanish took precedence and usually rendered many US citizens “foreign.”
By the turn of the century, “Mexicans” (whether natural-born US citizens or legal immigrants) had spread around the country. Even a 1908 US Labor report noted, “an increasing number of Mexicans were living outside the Southwest.” By the 20’s they could be found as far away Minnesota, Chicago, Detroit, even Alaska.
Over the next decade news of the INS and Border Patrol in El Paso and Texas started to spread. Anti-immigrant activists like Roy Lawrence Garis, began publishing articles and books proclaiming a “Mexican invasion.” National sentiment changed overnight on October 29th, 1929. The stock market crash, known as Black Tuesday, officially rang-in the beginning of the Great Depression. Rather than blame brokerage firms, rising interest rates, or the gold standard, Mexicans were seen as a main contributor.
The following year, when Census officials began their usual tabulation of residents, there was one monumental change. For the first (and last) time, the US Census added “Mexican” as a classification of race. In the years that followed, the United States initiated an ethnic cleansing across the country. By 1936, almost 2,000,000 “Mexican-raced” people were deported as part of a “Mexican Repatriation” initiative by President Hoover. Some estimate over 80% were in fact US citizens. During this period, nearly half of the Hispanic population of California was removed.