On Wednesday, Norman Lear, one of the most successful men television has ever seen, turned 100. It is difficult to overstate the influence of the producer behind shows such as “All in the Family,” “Maude,” “Sanford and Son,” “Good Times,” “The Jeffersons” and more. In fact, in the mid-1970s, Lear produced half of the 10 highest-rated shows on the air — with one estimate putting the cumulative weekly audience at more than 120 million viewers.

Yet Lear’s influence was not just a question of popularity. He also reshaped television entertainment by fostering open conversations about segregation, racism, sexual violence and abortion. In particular, “All in the Family” — the most popular program on television for an unprecedented five seasons — made politicians, activists and advocates take note and strategize how to use the show to promote their own agendas. In short, Lear took advantage of a changing television industry and shifting political landscape to remake both realms.

Lear was not the first producer to tackle hard subjects. In the 1950s, Rod Serling, of “Playhouse 90” and “The Twilight Zone” fame, made a name for himself as television’s “angry young man.” A decade later, brothers Tom and Dick Smothers turned their “Comedy Hour” variety show into a forum for biting satire and antiwar messages. More often than not, however, networks’ standards and practices departments (the industry euphemism for censors) made sure no controversy made it onto prime-time television in the 1950s and 1960s.

During this period, Lear wrote for shows like the “Ford Star Revue,” “The Colgate Comedy Hour” and “The Martha Raye Show.” By the 1960s, he teamed up with Bud Yorkin, a respected television director and producer, to form Tandem Productions and focus on television specials and motion pictures. In 1967, Lear scored an Academy Award nomination for best original screenplay for the Yorkin-directed “Divorce American Style.”

When Lear heard about a groundbreaking television show in the United Kingdom called “Till Death Us Do Part,” about a raucous, combative household, he recognized his own experiences growing up. Lear decided to return to television comedy and pitch a sitcom that would eventually be known as “All in the Family.” ABC, the weakest of the three networks, rejected two separate pilots before Lear struck gold when CBS, the No. 1 network, decided to take a chance on the potentially divisive show.

Lear’s pitch came at a fortuitous time, because CBS was just starting to rethink the “least objectionable programming” philosophy that had long shaped television’s business strategy: Avoid offending viewers, the theory went, and a network would succeed. The result? Quiz shows, westerns and escapist comedies about talking horses, flying nuns and the small town-charm of Andy Griffith’s Mayberry.