Robby Robinson, a wedge of black marble, arrived in Venice Beach in 1975 with one oversize suitcase and seven dollars. That was every dime he had after quitting his job and selling everything of value but the trophies he’d won at bodybuilding shows in the Jim Crow South. He’d left behind a wife, three small children, and a certain localized fame as the best-ever body in the state of Florida, fronting 20-inch biceps, a 28-inch waist, and 205 pounds of peaked, freak muscle on his hourglass, 5-foot-8 frame. But if your dream back then was to make the cover of Muscle Builder and storm the palace of giants in your sport, there was one thing to do and one place to do it: Join Gold’s Gym in Venice Beach. With the ocean at its back, the sun through its skylights, and the biggest men on Earth trooping in by the dozen to bench 450 before breakfast, Gold’s was Camelot-by-the-shore. You felt its pull in your hyper­trophied heart, deep in the belly of that reckless muscle.

Robinson, born and raised in the swamps of Tallahassee by an illiterate mother and a bootlegging father who later abandoned his 14 children, had a deep and perfectly rational terror of whites. Driving to shows in Mississippi and Georgia, he had seen the signs posted on rural light poles: niggers, don’t get caught here come sundown. But it was a letter from a white man that had brought him to Venice: a written invitation from no less than Joe Weider, the publisher of Muscle Builder, to come out and join his stable of champion bodies living and training large in Los Angeles. Robinson got off the plane expecting to be met by Weider, or if not by him then by Arnold Schwarzenegger, Weider’s Austrian prince, who’d won the title of Mr. Olympia five times running. Neither showed up, though, and after standing around for hours, Robinson tossed the suitcase over his shoulder and walked nine miles to Venice in platform heels.

He found a place to crash at a fellow bodybuilder’s and showed up at ...