The proposition was simple enough: Give the sidekick of a successful sitcom a separate show, and get another successful (and easy to produce) sitcom in return. But the simple act of giving Mary Tyler Moore her own series — even one with a premise not so far removed from the show that made her famous — proved a quiet revolution. The Mary Tyler Moore Show changed television, plainly and permanently. So did the woman who carried it, who passed away on Wednesday at the age of 80.

Moore’s first iconic role was on The Dick Van Dyke Show, Carl Reiner’s semi-autobiographical series about the backstage lives of comedy writers. Moore’s character wasn’t one of them, of course; she played one of the wives, holding down the fort in scenic Westchester while her husband, played by an actor 11 years her senior, wrote jokes in the city. Still, her five-season performance was enough to earn an Emmy, name recognition, and the clout to anchor her own series. The Mary Tyler Moore Show premiered on CBS in September 1970.

Like Dick Van Dyke, Mary Tyler Moore was a workplace sitcom about behind-the-scenes shenanigans in the television industry. Unlike Dick Van Dyke, the professional at its center was a woman, and unmarried, too. Moore’s Mary Richards arrived in Minneapolis and took a job as an associate producer at a local news station after the breakup of a long-term relationship; the CBS research department vetoed a divorce in the original pitch. Mary Richards was also 30, several years younger than Moore herself but still boundary-pushing for a female lead, let alone one without a partner. Put plainly, she was unprecedented, which might be why critics (who initially panned the series) and network schedulers (who put it up against The Don Knotts Show) alike had no idea what to do with the show until audiences started catching on. By its second season, Mary Tyler Moore had won an Emmy (it would eventually win three Outstanding Comedy Series awards in a row). By the end of that season, the show had climbed from no. 22 in the ratings into the top 10.

Mary Tyler Moore was followed by the likes of Murphy Brown, Sex and the City, and 30 Rock, but it was the first series with what passes today for an utterly banal setup: a woman with a professional and personal life and without a nuclear family. The show premiered just as the women’s liberation cause started to break off from the leftist activism of the ’60s into a movement in its own right, and it was one of the first pieces of popular culture to reflect those values.

It would be an exaggeration to call Mary Tyler Moore explicitly feminist; Richards always called her overbearing boss “Mr. Grant” when everyone else called him “Lou,” and Moore never subscribed to the label in real life. Yet one of the show’s greatest lessons was that a show didn’t have to espouse a particular set of norms so long as it embodied them. Mary Tyler Moore was a contemporary of more brazen social-issues shows like Maude and One Day at a Time, and while it was less outspoken on subjects like therapy and abortion, the show included an explicitly gay male character and passing references to the birth control pill. Mary Tyler Moore was arguably more political than its reputation might imply.

The show walked the walk off camera as well as on. Though the series was cocreated by James L. Brooks and Allan Burns, Moore didn’t simply front her eponymous show. She also produced it under the banner of MTM Enterprises, the company she cofounded with her then-husband, television executive Grant Tinker. (Tinker died last fall at the age of 90.) Moore had a financial stake in the show as well as a simple professional one, making her a forerunner to performer-producers like Tina Fey as well as characters like Liz Lemon. In MTM Enterprises’ formidable post-Moore CV, which included spinoffs Rhoda and Lou Grant as well as Hill Street Blues and St. Elsewhere, one can see shades of über-producers like Shonda Rhimes.

Beyond Moore, the show also opened up opportunities further down the creative masthead. By 1973, a full third of its writers were women — less than one might hope for given its subject matter was rooted in the female experience, but still unheard of at the time. They included Treva Silverman, who won an Emmy for Outstanding Writing in a Comedy Series for the fourth-season episode “The Lou and Edie Story” in 1974; she was the first woman to win the award for sole credit on a script. Mary Tyler Moore was a crucial juncture in the professional lives of real women even as it showed millions of people what it was like to live that life each week.

Mary Tyler Moore wasn’t perfect. Feminists at the time criticized Mary Richards for being too passive, and to watch the show’s first few seasons on Hulu is to step into a time capsule; “progressive for its time” still means “behind ours.” But few first drafts are perfect. What matters is the chain reaction it started. Mary Richards stumbled so that Murphy Brown could scramble, Carrie Bradshaw could wonder, and Hannah Horvath could flounder. Mary made it after all, and so did they. So will we.