Betty White, who created two of the most memorable characters in sitcom history, the nymphomaniacal Sue Ann Nivens on “The Mary Tyler Moore Show” and the sweet but dim Rose Nylund on “The Golden Girls” — and who capped her long career with a comeback that included a triumphant appearance as the host of “Saturday Night Live” at the age of 88 — died on Friday December 31 2021 at her home in Los Angeles. She was 99. Ms. White was over 50 and already a television veteran when she first appeared on “The Mary Tyler Moore Show,” but her work there elevated her career to a new level. Betty Marion White was born on Jan. 17, 1922, in Oak Park, Ill., the only child of Horace and Tess (Cachikis) White. Her father was an electrical engineer, her mother a homemaker. When Betty was a toddler, the family moved to Los Angeles, where she grew up. At Beverly Hills High School, from which she graduated in 1939, she appeared in several student productions and even wrote her class’s graduation play. She also met and married a P-38 pilot, Dick Barker. That marriage lasted less than a year. Lane Allen, an actor turned agent, encouraged Ms. White to pursue an acting career. She and Mr. Allen were later married, but that union also ended in divorce. Ms. White began her radio career by saying one word on the popular comedy “The Great Gildersleeve.” The word was “Parkay,” the name of the margarine sponsoring the show. She broke into television in 1949 on a local talk show called “Al Jarvis’s Hollywood on Television.” When Mr. Jarvis left the show, she succeeded him as host. by the early 1960s she was best known as a very busy freelance guest. Game shows were her specialty: She appeared on “To Tell the Truth,” “I’ve Got a Secret,” “The Match Game,” “What’s My Line?” and, most notably, “Password,” whose host, Allen Ludden, she married in 1963. Ms. White and Mr. Ludden remained married until his death in 1981. White and Ludden had no children together, but she helped him raise his three children by a previous marriage, David, Martha and Sarah. Ms. White had a longstanding interest in animal welfare. She devoted time and money to organizations like the American Humane Association and the Fund for Animals.