Answer by taking a quote from the following article:

John William Carson (October 23, 1925 - January 23, 2005) was an American television host, comedian, writer, and producer. He is best known as the host of The Tonight Show Starring Johnny Carson (1962-1992). Carson received six Emmy Awards, the Television Academy's 1980 Governor's Award, and a 1985 Peabody Award. He was inducted into the Television Academy Hall of Fame in 1987.

Carson began his broadcasting career in 1950 at WOW radio and television in Omaha, Nebraska. Carson soon hosted a morning television program called The Squirrel's Nest. One of his routines involved interviewing pigeons on the roof of the local courthouse that would report on the political corruption they had seen. Carson supplemented his income by serving as master of ceremonies at local church dinners, attended by some of the same politicians and civic leaders whom he had lampooned on the radio.  The wife of one of the Omaha political figures Carson spoofed owned stock in a radio station in Los Angeles, and in 1951 referred Carson to her brother, who was influential in the emerging television market in southern California. Carson joined CBS-owned Los Angeles television station KNXT. In 1953, comic Red Skelton--a fan of Carson's "cult success" low-budget sketch comedy show, Carson's Cellar (1951 to 1953) on KNXT--asked Carson to join his show as a writer. In 1954, Skelton during rehearsal accidentally knocked himself unconscious an hour before his live show began, and Carson successfully filled in for him. In 1955, Jack Benny invited Carson to appear on one of his programs during the opening and closing segments. Carson imitated Benny and claimed that Benny had copied his gestures. Benny predicted that Carson would have a successful career as a comedian.  Carson hosted several shows besides Carson's Cellar, including the game show Earn Your Vacation (1954) and the CBS variety show The Johnny Carson Show (1955-1956). He was a guest panelist on the original To Tell the Truth starting in 1960, later becoming a regular panelist from 1961 until 1962. After the prime time The Johnny Carson Show failed, he moved to New York City to host Who Do You Trust? (1957-1962), formerly known as Do You Trust Your Wife?. In 1958, he appeared as a guest star in an episode entitled "Do You Trust Your Wife" on NBC's short-lived variety show, The Polly Bergen Show. On Who Do You Trust?, Carson met his future sidekick and straight man, Ed McMahon. Although he believed moving to daytime would hurt his career, Who Do You Trust? was a success. It was the first show where he could ad lib and interview guests, and because of Carson's on-camera wit, the show became "the hottest item on daytime television" during his five years at ABC.

When did Johnny start his television career?
1950