Letterman was born in Indianapolis, Indiana. After attending Ball State University, in Muncie, Indiana, Letterman began work as a local weekend television meteorologist and radio talk show host. He received local recognition for his unpredictable on-air behavior, which included erasing state borders from the weather map and predicting hail stones "the size of canned hams". In 1969, Letterman married his college sweetheart, Michelle Cook. The couple divorced in 1977.
In 1975, Letterman moved to California, with hopes of becoming a comedy writer. He began performing at The Comedy Store, a famed Los Angeles comedy club and proving ground for young comics. His dry, sarcastic humor caught the attention of talent scouts for Johnny Carson's Tonight Show, and soon Letterman was a regular guest on the show.
After stints as a cast member on Mary Tyler Moore's variety show and guest appearances on sitcoms such as Mork And Mindy, Letterman was given his own morning comedy show on NBC. The show was critical success, winning two Emmys and receiving 5 nominations, but ended up being a ratings disappointment, and was cancelled after a brief run during the summer of 1980. However, NBC kept Letterman under contract, and in 1982, his Late Night with David Letterman first appeared on the network.
Letterman's show, which ran late on weeknights immediately following The Tonight Show, quickly established a reputation as being edgy and unpredictable, and soon developed a cult following. The show was markedly different than the soft-sell talk-show competition, and Letterman the interviewer could be sarcastic and antagonistic, to the point that a number of celebrities have even stated that they were afraid of appearing on the show. Letterman's reputation as a testy interviewer was born out of moments like his verbal sparring matches with Cher, Madonna (described by comedian Robin Williams as a "battle of wits with an unarmed woman"), and Shirley MacLaine. The show often included quirky, genre-mocking regular features, such as "Stupid Pet Tricks" and a facetious letter-answering segment on Fridays. Other memorable moments included Letterman using a bullhorn to interrupt the Today Show TV program, which was on the air conducting a live interview at the time, announcing that he was not wearing any pants; interupting the local news by walking into their studio; and the outrageous appearances by comedian Andy Kaufman and comic book writer, Harvey Pekar. In one highly publicized appearance, Kaufman appeared to be slapped and knocked to the ground by professional wrestler Jerry Lawler. (Lawler and Kaufman friend Bob Zmuda later revealed that the event was staged). Letterman also made use of the Manhattan location of his CBS studio, often staging comedy bits on the streets and businesses surrounding the theater.
In 1985, Letterman established the Letterman Telecommunications Scholarship at Ball State University, to provide financial assistance to Department of Telecommunications students, based solely on his or her creativity, and not on grades.
For a time, Letterman was engaged to Late Night head writer, Merrill Markoe, but the relationship eventually fell apart. Markoe moved to California soon after to pursue a writing career.
In 1988, Margaret Mary Ray was arrested while driving Letterman's Porsche near the Lincoln Tunnel in New York City. Ray claimed to be Letterman's wife. Ray went on to be arrested repeatedly in subsequent years on trespassing and other counts. In one instance, police found her sleeping on Letterman's private tennis court at his home in New Canaan, Connecticut. Ray spent nearly 10 months in prison and 14 months in a state mental institution for her numerous trespassing convictions. On October 7, 1998, Ray was struck and killed by a train in an apparent suicide in Colorado.
Letterman remained with NBC for 11 years. When Johnny Carson announced that he would retire in May of 1992, a protracted, multi-lateral battle erupted over who would replace the long-time Tonight host. Eventually, executives at NBC announced Carson's frequent guest-host Jay Leno as Carson's replacement. Letterman, who was Carson's personal protege and who had frequently credited Carson with boosting his career, was reportedly bitterly disappointed and angry at not having been given the Tonight Show job which he claimed to have been promised many years earlier. In 1993, after receiving advice from Carson, Letterman moved to CBS, as host of The Late Show with David Letterman. The Late Show competes in the same 11:30 pm (10:30 pm in some areas) time slot as Leno's The Tonight Show. The ratings battle between the two talk shows had several ups and downs, with Leno carrying the timeslot most often while Letterman won critical praise and Emmy awards. In 1996 U.S. pay television service HBO produced a made-for-television movie called "The Late Shift", based on the book by Bill Carter, chronicling the battle between Letterman and Jay Leno for the coveted Tonight Show hosting spot.
Letterman started his own production company, Worldwide Pants Incorporated, which has produced the popular TV series for CBS, notably Everybody Loves Raymond and several critically acclaimed (but short lived) television series for Bonnie Hunt.
In January of 2000, Letterman underwent quintuple heart bypass surgery at New York Presbyterian Hospital after an angiogram revealed one of his arteries was seriously constricted. Friends of Letterman guest hosted reruns of the Late Show (which was called The Late Show Back Stage) in his absence, including Drew Barrymore, Ray Romano, Robin Williams, Bill Murray, Kathie Lee Gifford, Regis Philbin, Charles Grodin, Julia Roberts, Bill Cosby, Bruce Willis, Jerry Seinfeld, Martin Short, Danny DeVito, Steve Martin and Sarah Jessica Parker.
Upon his return to the show on February 21, 2000, Letterman brought onstage all of the doctors that had performed the operation, including Dr. O. Wayne Isom and physician Louis J. Aronne, who makes frequent appearances on the show. In an unusual show of emotion, Letterman was nearly in tears as he thanked the doctors. The episode earned an Emmy nomination.
On September 17, 2001, David Letterman was the first major American comedy performer to return to the television airways after the September 11, 2001 Terrorist Attack. In his opening monologue, a deadly serious and very emotional Letterman struggled with the reality of the attacks and the role of comedy in a post-9/11 world, saying, "We're told that they were zealots fueled by religious fervor... religious fervor... and if you live to be a thousand years old will that make any sense to you? Will that make any goddamn sense?"
In March 2002, as Letterman's contract with CBS was expiring, ABC expressed the intention to offer Letterman the time slot for long-running news program Nightline with Ted Koppel, citing more desirable viewer demographics. This caused a minor flap that ended when Letterman re-signed with CBS and offered public apologies to Koppel.
Letterman, along with bandleader Paul Shaffer and Late Show stage hand, Biff Henderson, celebrated Christmas 2002 in Afghanistan with United States and international military forces stationed in the country.
In late February 2003, Letterman was diagnosed with a severe case of Shingles. As a result, and for the first time since his bypass surgery, Letterman handed the reins of the show to several guest hosts including actor Bruce Willis, former professional tennis player John McEnroe, Morning talk host Regis Philbin and several other prominent Hollywood performers.
On September 12, 2003 the 56 year old David announced on the late show that his long term girlfriend and ex-colleague Regina Lasko, born 1960, is six months pregnant with his child. His son Harry Joseph Letterman, named after his late father, was born on late Monday night, November 3, 2003. He weighed in at 9 pounds, 11 ounces and is 21 inches long, Letterman announced on his show Tuesday night. Monday's show was hosted by Paul Shaffer in David's absence.