That venerable, inimitable, sloppy palace of bad decisions The EndUp was born 50 (and a half) years ago, and they’re now getting around to celebrating — appropriately kinda late — with a Union Square takeover dance party.

Once upon a time in an era of SoMa dominated by leather and country-and-western bars (The Stud, after all, began as a country-and-western themed bar, hence the double-entendre name), The EndUp was born. It was actually born in mid-November 1973, as a sibling establishment to The RoundUp, a western bar one block up 6th Street, owned by Al Hanken and Greg Loughner.

The bar was primarily gay from the 70s into the 90s, becoming known starting in 1974 for its Jockey Shorts Dance Contest — which was featured in Armistead Maupin’s Tales of the City column in the Chronicle and subsequently featured in the PBS mini-series based on the first book of those columns.

It was always known as a big dance bar with indoor and outdoor spaces, and as an after-hours club — and the latter has made it legendary in an IYKYK kind of way.

In the 90s, it was home to the legendary Club Uranus, which birthed such stars as Justin Vivian Bond, Heklina, Kitty Litter, and Trauma Flintstone. And Fag Fridays launched in 1996 and ran through 2008, featuring an array of LGTBQ club DJs from the Bay Area including Ellen Ferrato and resident DJ David Harness.

After a series of ownership changes and the demise of those weekly LGBTQ events, the club became more mixed and attracted various crowds to events like Sunrise Sunday. And some bad vibes arrived in 2016 with two separate fatal shooting incidents that could have threatened the club’s existence — one in June 2016 that took place inside the club, and one that took place outside in October 2016.

But The EndUp has endured, it was granted Legacy Business status by the city in 2019, and Saturday, June 15 will be a big 50th birthday bash in Union Square — potentially drawing a pretty huge crowd.

Given that the actual birthday was seven months ago, the Facebook invite just calls this party a “fashionably late” one.

“Known as San Francisco’s most legendary after-hours nightclub and premier day-club, @endupsf celebrates dance culture fifty years strong since 1973,” the club says.

DJs include Oscar G, Paul Goodyear, Dean Samaras, Brian Salazar, and Hawthorne. (See the DJ bios here.)

The free party in Union Square runs from 1 pm to 9 pm, Saturday — and, of course, the party continues at The EndUp after that, with DJ Oscar G doing an encore set, joined by DJs Hawthorne, Steve Fabus, and more.