Anniversary journalism is often a waste of time–there’s little to learn from the 40th birthday of the Big Mac–but occasionally it’s a tool for re-education. Recently I watched the new PBS series on the history of the Warner Bros. Studios, which is celebrating its 75th year. Titled “You Must Remember This,” directed by film scholar Richard Schickel and narrated by Clint Eastwood, the five-hour American Masters presentation is a treat, not least because it reminds us that in the Golden age of Hollywood, the various studios had distinct styles–and philosophies.

MGM, which I learned to love through the late-night “Bijou Picture Show” on Channel 4 in the ’70s, was the studio for lavish entertainments with larger-than-life stars. MGM had class. But Warner Bros. was the studio of class struggle. It made movies for the working class and about the working class. Warners’ Depression-era films were raw and racy, unafraid to address the realities of poverty, prostitution and drug addiction. Its big star of the 30s was Jimmy Cagney, the tough guy toe-tapper. (Later it was the studio of Humphrey Bogart and James Dean.)

Nowadays, the movie studios aren’t family operations and don’t reflect the eccentric tastes of their founders. Still, it behooves us to know which clan or conglomerate is funding our entertainment. The contemporary Warner Bros., a division of Time Warner (nee AOL-Time Warner) is now associated with “event” movies (AKA “tentpole pictures”) like the “Harry Potter” and “Batman” flicks. But it’s still got a feistiness and independence that I think Jimmy Cagney would respect. This is the studio that dared to distribute “Good Night and Good Luck,” “In the Valley of Elah” and “A Scanner Darkly.” If “Batman” movies can subsidize such provocations, I hope that Warner Bros. lasts another 75 years.