Nearly 45 years after it premiered, “The Rocky Horror Picture Show” still plays in more than 80 U.S. towns and cities every weekend of the year. That success is nothing less than a movie miracle.

When it was released in 1975, the movie did so poorly that the New York run was canceled before it began. And then someone noticed that “The Rocky Horror Picture Show” had all the ingredients of a midnight movie — it was risqué, raucous and a little bit trippy. The film was installed as the late show at the Waverly Theater in Greenwich Village, and something unexpected happened: people started talking back to the movie, shooting water pistols and throwing toast, and even dressing up like the characters and shadowing their moves in front of the screen.

Thanks to Tim Curry’s gloriously over-the-top portrayal of Frank N. Furter, the film’s seductive, pansexual lead, those midnight screenings became a sanctuary for people who saw themselves as outsiders, especially queer and gender-nonconforming people. No longer mere movie-goers, they became a tribe and kept coming back, week after week.

These days, going to see “The Rocky Horror Picture Show” is an exercise in nostalgia — the callouts that audience members once competed with each other to create are now calcified into a script that is easily found online, which means it’s almost impossible to add anything new or topical. What was once transgressive is now a tradition, but one that shows no sign of ending any time soon.

American Icons is made possible by a grant from the National Endowment for the Humanities.