This week, the world looked on in shock, despair, and outrage as US Immigration and Customs Enforcement enacted a new immigration policy that can be described only as ghoulish, separating children, including babies, from their parents, and placing them in unmonitored, unsafe detention facilities. (Donald Trump’s executive order, which he claimed would address the problem, will likely only make things worse.)

There has long been a stark, racial element to how Americans—and especially our current president—talk about immigration. For a quick elucidation of how this has worked in the case of Mexican folks in America, we turn to Gregory Smithsimon’s intensely smart Cause… And How it Doesn’t Always Equal Effect, which we were pleased to publish back in February.

This is from Chapter 3, “What Race Will the White Minority Be?”:

Eligibility for citizenship—painted as whiteness—has remained a category since its inscription in the Constitution, but those eligible for membership in that group has changed since then. Studies of race have most often used the changing racial categorization of immigrants as evidence of the changing definition of whiteness. Groups like Germans, Irish, Italians, and Jews were popularly defined as noncitizens and non-white when they first arrived, and then became white. Certainly, this process is revealing. But in addition to the domestic influences on the boundaries of whiteness, international relations have also altered racial categories.…

The case of Mexicans and Mexican Americans offers some indication of how war brought greater whiteness. The racial classification of Mexicans and Mexican Americans has been one of the most unstable racial projects in the United States. At times white, at times Native American, and at times part of a distinct “Hispanic” race, these shifts have not been at random. Mexicans have been most white when Mexico was a powerful threat, least white when Mexico has been least powerful.

Given the recent hostility of elected Texas officials toward Mexican immigrants, it is noteworthy that in the mid-1930s, Texas law (and federal law) made clear that Mexicans were white. Mexicans in Texas could vote in whites-only primary elections. This was only eighty years after the conclusion of the Mexican-American War of 1846–1848. When the California Constitution was written a year later, even the proslavery framers felt compelled by the treaty with Mexico to expand voting rights to “white citizens” of both California and Mexico. In World War II, as historian Nell Irvin Painter points out, Blacks and Asians were segregated in the US military; Latinos served in white units.

Although the Treaty of Guadalupe Hidalgo that ended the Mexican-American War is still in force, its attendant racial project that rendered Mexicans white has ebbed and flowed. As Mexico receded as a powerful threat, subsequent state laws excluded Mexican children as nonwhite. (In one pointed exception, in 1931 California courts reversed a local Jim Crow ordinance and required that Mexican-American children be allowed to attend the new white school, because California law explicitly allowed for discrimination against Native Americans, Orientals, and Negroes. But Mexicans, the court concluded, were Caucasian and could not legally be barred from a school.) Later in the twentieth century, as Mexico itself became less of an adversary and more of a one-party state under US influence, Mexicans became less white in America.

Cause is on sale now. Buy your copy here, or at your neighborhood independent bookstore.