Contrary to what you might assume, America’s history of mandatory blood tests before marriage has nothing to do with an Oedipal fear of accidentally tying the knot with your long-lost mother, brother, or other close relative. It does, however, have roots in what was once considered a topic nearly as uncomfortable as incest: sexually transmitted diseases.

Back in the 1930s, the rising rates of syphilis were causing a public health crisis, partially because the subject was so taboo.

“We might virtually stamp out this disease were we not hampered by the widespread belief that nice people don't talk about syphilis, that nice people don't have syphilis, and that nice people shouldn't do anything about those who do have syphilis,” U.S. Surgeon General Thomas Parran Jr. wrote in a 1936 article called “The Next Great Plague to Go.”

So Parran launched a nationwide campaign to educate everyone about venereal disease, commonly abbreviated as “VD.” Posters, films, cartoons, and even stamps urged people to avoid casual sex and get tested regularly, while the American Sexual Health Association sponsored a “Social Health” exhibit at the 1939 World’s Fair in New York. In 1938, Congress passed the Venereal Disease Control Act, which distributed $3 million—and more in later years—among the federal and state governments for research and testing.

The Illinois Works Projects Administration wanted people to stick to gambling on whether the Chicago Cubs would ever win the World Series.Work Projects Administration Poster Collection, Library of Congress Prints and Photographs Division // No Known Restrictions on Publication

Though Parran’s efforts were progressive in some ways, they were seriously damaging in others. For one, he perpetuated misconceptions about how STIs could spread, asserting that “many cases come from such casual contacts as the use of a recently soiled drinking cup, a pipe or cigarette, in receiving services from diseased nursemaids, barber or beauty shop operators, etc.” He also oversaw a horrifically unethical experiment in Tuskegee, Alabama, that studied the effects of syphilis in several hundred Black men by withholding treatment from them, without their informed consent.

It was in this culture of heightened awareness (and misinformation) that states began to pass laws requiring couples to submit to blood tests before applying for marriage licenses, so they could avoid spreading a previously undetected venereal disease to their spouse and future children. As historian Erin Wuebker wrote in 2016, 30 states had enacted such legislation by 1944, and Gallup polls throughout the 1930s and 1940s revealed that the majority of American citizens supported the government initiatives.

New York's subway stations were filled with lovely posters like this in the late 1930s and early 1940s.Work Projects Administration Poster Collection, Library of Congress Prints and Photographs Division // No Known Restrictions on Publication

After the syphilis crisis was over, some states simply pivoted to using premarital blood tests to check for other diseases, like tuberculosis, rubella, and HIV. The problem, however, was that the practice didn’t actually uncover that many cases of any kind. The Mises Institute reported that the nation as a whole spent around $80 million on premarital syphilis tests and found only 456 positive cases; and according to a 1989 study in the Journal of the American Medical Association, prospective newlyweds in Illinois spent $2.5 million to test for HIV during the first six months of the program, and only eight of the 70,846 tests came back positive. Since neighboring states saw an increase in marriage license applications during that time, the study suggested that people were simply crossing state borders to avoid getting tested (after all, Illinois didn’t pay for the tests).

As states started to realize that premarital blood testing wasn’t a cost-effective way to screen for diseases, they abolished their laws. But it was definitely a slow process—Montana became the final state to repeal its mandatory blood testing (for rubella) just last year.

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