Thursday, December 5 marks the 80th anniversary of the 21st Amendment, which repealed Prohibition, and 21st Amendment Brewery is hosting a celebration. A parade starts at 4 pm in Justin Herman Plaza and ends at 21st Amendment Brewery on 2nd Street at Brannan, where an after-party will roll till 9 pm.

“If it weren’t for the passage of the 21st Amendment, we wouldn’t be in business,” says Shaun O’Sullivan, Brewmaster and co-founder of 21A. “Of course, neither would any other adult beverage maker, at least not legally. But since we’re named after the constitutional amendment that made our brewery possible, we thought we should celebrate.”

Some background: in January 1920 the 18th Amendment went into effect, criminalizing the manufacture, transportation and sale of intoxicating beverages. What was titled The Noble Experiment was a failure of epic proportion. Not only did organized crime get a huge boost during Prohibition, but America’s rich tradition of local brewing was decimated. Of the 1,392 breweries that existed before Prohibition, only 164 restarted afterwards. In 1933 the 21st Amendment went into effect, repealing Prohibition, and the long, slow march toward restoring our beer brewing traditions began.

For Thursday’s celebration, don you favorite Prohibition-era garb and join your fellow revelers for the start of the parade at Justin Herman Plaza, which will include a marching band and signs protesting the 18th Amendment. When the parade reaches the 21A Brewery, co-founders Shaun O’Sullivan and Nico Freccia will tap six special cask-conditioned firkins of beer, while an eight piece Dixieland band provides music. The upstairs Brewer’s Loft will be converted to a password-only fundraiser, complete with Prohibition-era cocktails and casino games. See 21A’s Facebook, Twitter and Instagram pages for the password.

Once you’ve entered the casino, you can exchange $20 for $500 worth of chips, which can be used to play roulette, blackjack and poker until 9 pm or until you bust. At 9 pm, gamblers can cash in their chips for raffle tickets, making them eligible for prizes of 21A shwag. All gambling proceeds benefit the Center for Youth Wellness.

The special cask-conditioned ales will be lined up on the main bar. Most of the firkins are provided by guest brewers including Speakeasy, Drake’s, Thirsty Bear and Magnolia. Complimentary scoops of Three Twins Ice Cream made with 21A’s Fireside Chat Winter Spiced Ale will also be served.

“I’ll be wearing a zoot suit, and many of our staff members will be wearing flapper dresses, fedoras, or bowler hats,” says Freccia. “So pick your favorite fashion decade from the Prohibition era, and come to the party all decked out. Or not. Either way, we’ll serve you beer.”