Mary Tyler Moore, whose two beloved TV characters, Laura Petrie and Mary Richards, helped redefine sitcoms in the 1960s and ‘70s and became icons for future generations, died today in Greenwich, Conn. She was 80.

Moore, whose influence can be seen in many sitcoms featuring single, working women, perhaps most notably in Tina Fey’s role as Liz Lemon on 30 Rock, died of cardiopulmonary arrest after contracting pneumonia.

While she successfully worked in film, theater and advertising beginning in the mid-1950s, she was best known as the co-star of The Dick Van Dyke Show from 1961-66 and star of The Mary Tyler Moore Show from 1970 to 1977.

She won two Emmys for her work with Van Dyke, creating a fashionable and witty comic housewife that advanced the sitcom from the stodgy and stagey shows of the 1950s that largely gave women the roles of wives and mothers that were subservient to men.

As Richards, for which she won four Emmys, Moore broached subjects that others ignored: female empowerment and independence, birth control and equal pay. The character-driven show was the first to have female characters as fully fleshed out as the males; it ushered in a modern era for the workplace sitcom.

Her brightest moment in film came in 1980 with Ordinary People, a role that earned her an Oscar nomination and a Golden Globe win. Between Van Dyke and MTM, she co-starred with Julie Andrews in Thoroughly Modern Millie and Change of Habit opposite Elvis Presley.