The late comedian George Carlin - famous for those "Seven Words You Can Never Say on TV" - was honored Monday with the Mark Twain Prize for American Humor, the only award he saw as a legitimate comedy prize. Jon Stewart, Lily Tomlin, Joan Rivers and others saluted Carlin at the John F. Kennedy Center for the Performing Arts for inspiring their own comedy, and they took up his cause of pushing the boundaries of free speech. On the red carpet before the show, Stewart said he was about 10 years old when Carlin's album Class Clown was released. Stewart said it made him the funniest kid at school until his friends also found Carlin's work. "For all his antiestablishment cred, he was a working man. He punched in. He sat down and he wrote," Stewart said. "He respected what he did." The prize was announced shortly before Carlin died of heart failure in June at the age of 71. This is the first time in its 11 years that the award was presented posthumously. The program will be aired later on PBS stations. "He was thrilled," Carlin's daughter, Kelly Carlin McCall, told The Associated Press shortly before the award ceremony. "I think he represented a lot of what Mark Twain did for our country, not only being smart and funny but also being a sharp commentator." The Twain Prize was instituted in 1998 and first given to comedian and actor Richard Pryor. Recent recipients have included Billy Crystal in 2007 and Steve Martin in 2005. Carlin had great respect for the prize and its previous honorees, said Jerry Hamza, Carlin's longtime manager and best friend. Carlin "always flipped" over the comedy of Tomlin and Pryor, two previous recipients. "He would have been humbly grateful," said Hamza. "Also George, who throughout his career was perceived as an outsider or maverick, had a real desire to connect with other comedians. He loved being in that club." Carlin's career as a comedian, actor and author spanned more than 50 years. He was paired for a brief time with longtime friend Jack Burns, then went solo in 1962, embracing the counterculture movement of the era. He would record 23 comedy albums, win four Grammys, serve as the first host of Saturday Night Live and make more than a dozen TV specials for HBO. His "Seven Words" routine was arguably his most famous. It was the subject of a US Supreme Court ruling on free speech that upheld the government's right to sanction broadcasters who air offensive language when children might be listening. Carlin remained active right until his death, and his 14th and final HBO special, It's Bad For Ya, in which he mocks death, is scheduled for release on DVD on November 25. His 1984 album Carlin on Campus was rereleased earlier this month. Many of the comics, including Bill Maher, used the recent election and the ceremony's proximity to the oval office as fodder for a slew of politically charged jokes. "It's a great day to be an American again. We have a president who can speak English,""Maher said, jabbing President Bush's famous verbal flubs. Though Carlin said he didn't vote in presidential elections, he was a keen political observer and commentator. "On certain things you'd call him a lefty," Hamza said. "On other things, you'd be surprised how conservative he might be."