As we look back at the Immigration and Nationality Act of 1965 and its impact on the United States, it is worth considering what the country looked like in the census year of 1970, before the major demographic effects of the act were felt.

For most of its history, the U.S. was a European-derived nation with a small African-origin minority, and 1970 was no different. The country was 84 percent white, 11 percent black, and just 4 percent Hispanic. Although Mexican immigration (both legal and illegal) had been increasing since the end of the Bracero program in 1964, Mexican Americans were still less than 3 percent of the population, with many claiming U.S. ancestry stretching back to the Mexican-American war.

The absence of Asians, who were mostly banned from immigrating before 1965, is especially striking. Just 0.7 percent of Americans were of Asian ancestry in 1970, with more than two-thirds of the total from China and Japan. Indians, Koreans, Vietnamese, and Filipinos, so common in American life today, were minuscule in number.

Also notable is how few immigrants lived in the U.S. at the time. At just 4.7 percent, the foreign-born portion of the population was at a historic low point in 1970. A half century earlier, the foreign-born stood at 13.2 percent, but the combination of legal restriction, depression, and war slowed immigration to a trickle. Of those who were foreign-born in 1970, about three quarters were white, with Germany, Italy, and Canada sending the most immigrants. In a preview of future immigration, however, Mexicans (8 percent) and Cubans (4 percent) were also well represented among the nation’s foreign-born.

Overall, the U.S. was still a relatively homogeneous place in 1970, with stirrings of Hispanic immigration but no major change to its historic white-black demographic. It is sometimes argued that the nation’s homogeneity was a mirage because of intra-white differences. But while it is certainly true that Southern and Eastern European immigration during the Great Wave of 1890-1920 caused social disruption, powerful assimilation forces fell upon the white American population in the ensuing years. Researchers generally credit both external events (the immigration cut-off in 1924, the shared experience of depression and war), and the characteristics of immigrants themselves (mostly European and Christian, like the native population) for the rapid assimilation.

By 1970, “white ethnics” were rapidly becoming simply “white.” For example, 85 percent of white Americans said they spoke only English at home in 1970. German was the second most common language, but it was spoken by only 3.7 percent of whites. Just 2.5 percent spoke Italian. In addition, the economist George Borjas once examined the persistence of ethnic earnings and education differences over time. He found a correlation between the socioeconomic status of an ethnic group in 1910 and its status around 1990. However, the relationship shrank to insignificance when Mexicans were excluded from the analysis. He observed strong (although not total) socioeconomic convergence among the European ethnic groups.

In contrast to the intergenerational assimilation of “white ethnics,” Hispanic Americans do not appear to be on the same path to economic parity. The children of Hispanic immigrants outperform their parents, as would be expected of a generation that had a chance to grow up in America. However, assimilation seems to stop there, with little to no further progress in the subsequent generations. Third-generation Hispanics remain well behind white Americans on measures of income, education, occupational status, and net worth. There is little evidence suggesting this situation will improve any time soon.

It is regrettable that, after largely achieving the long and difficult assimilation of Great Wave ethnic groups, the U.S. so quickly loosened its borders again, this time to take on an even greater assimilation challenge. The 1965 Act did not immediately open the flood gates, as some have alleged. Its long-term effects came through an emphasis on family reunification. Immigration from Latin America, which had already been growing before the Act, was amplified by family-based “chain migration.” Rather than address the problem of chain migration, politicians exacerbated it by giving amnesty to illegal immigrants in 1986, and then raising the visa caps in 1990. Every new legal immigrant became a possible source of exponential immigration growth.

In that sense, the 1965 Act was not the watershed moment that ended the homogeneity the U.S. had achieved by 1970. It was merely the first in a long series of measures that created the multi-cultural America of 2015.