Starring Sean Penn, Josh Brolin, and James Franco. Rated PG.

Sean Penn delivers a career-topping performance as Harvey Milk, the San Francisco politician gunned down, along with progressive mayor George Moscone, by an unstable colleague in 1978. (The film begins with board of supervisors president Dianne Feinstein’s stark announcement of the deaths on the steps of City Hall.)

Although the image of San Francisco as a gay mecca is now firmly entrenched—Republicans remind us in every election cycle—its arrival at something like self-determination was only recently achieved. This was in no small part due to the tireless efforts of a flamboyantly out former insurance salesman from New York City who only hit the West Coast eight years earlier.

At 128 minutes, the film suffers from the usual biopic compression, and there’s a little too much foreshadowing and thematic repetition, especially for a director as willfully experimental as Gus Van Sant. (As an expository device, our troubled hero narrates into a Dictaphone near the end of his life.) If anything, the maker of My Own Private Idaho, working from a fairly conventional script by Dustin Lance Black, could have splashed out a little more in his re-creation of the Castro district of the butterfly-collared ’70s.

Mostly, Van Sant lets his large and impressive cast do the work of conveying this unique time and place, with his subject the fiery catalyst who helped turned a shadowy subculture into a main-street phenomenon—and reactionary target. James Franco is the more passive partner who accompanied Milk across the country; Emile Hirsch and Toronto’s Alison Pill make strong impressions as loyal activists; and Josh Brolin—fresh off his success as a more genial psychopath in W.—is incendiary as Dan White, the Twinkie-fed supervisor who smoulders with resentment at Milk’s successes. (Diego Luna is darker as Milk’s subsequent lover.)

The movie’s greatest achievement, however—coming in the wake of Barack Obama’s ascendancy and California’s Proposition 8—is in making the events of 30 years ago joyfully, and painfully, relevant to everything happening today.