There have been a few (surprisingly few) same-sex couples who have tried to get legally married prior to the 21st century. Probably the most famous couple was that of Richard John Baker and his partner from the Baker v Nelson case in Minnesota that all the SCOTUS briefs from the opposing side keep mentioning. But, there is another couple who wanted their marriage recognized by the US in 1975.
From Vox.com:
The letter — which states, "You have failed to establish that a bona fide marital relationship can exist between two faggots" — was in response to Richard Adams and Anthony Sullivan, one of the first gay couples in the nation to try to get their marriage recognized by the federal government. A renegade clerk in Colorado married the couple in 1975, and they tried to use the marriage so Sullivan, an Australian, could remain in the country. The Justice Department flatly rejected their request
The letter from a district director at the Justice Department's Immigration and Naturalization Service is posted below.
It's difficult (if not impossible) to imagine a US government agency responding in this manner to a same-sex couple today. It shows how far the US government has come on gay rights issues, and especially the marriage equality issue under the Obama administration.
The Washington Post has the couple's story.
Sullivan and Adams met on Cinco de Mayo 1971 at a gay bar called the Closet in downtown Los Angeles. They made plans to meet the next day at Greta Garbo’s Hollywood Walk of Fame star on Hollywood Boulevard, and they were pretty much together for the next 41 years.
“I never met another person I fitted so well with,” says Sullivan. “Not to get sloppy, but he meant everything to me, and I meant everything to him.”
But there was a problem bigger than being openly gay in 1971. Although Adams was a naturalized citizen — his Filipino mother married an American when Adams was 12, and they moved to the United States — Sullivan was Australian. He was on a world tour when he first landed in Los Angeles on a tourist visa.
They saw a story in the Advocate about a woman named Clela Rorex, a young feminist county clerk in Boulder, Colo. One day not long after she took office, a gay couple asked whether they could marry. She checked the law and didn’t see anything that said they couldn’t. She asked a county attorney, and he couldn’t find anything, either.
I can't copy the entire story here, but it's definitely worth a read.