Steve Allen's zany spontaneity turned "Tonight" into an unexpected hit, but Jack Paar and Johnny Carson transformed late night into a television staple.

Johnny Carson deftly navigated the turbulent 1960s to elevate "The Tonight Show" and became the undisputed king of late night.

In the 1980s, David Letterman reinvented late night for a new generation and endless speculation began on who would be Johnny Carson's eventual successor.

Johnny Carson's 1992 retirement kicked off an epic late-night war between Leno and Letterman while newcomers Conan O'Brien and Jimmy Fallon emerged.

As the 2000s approached, diverse voices like Chelsea Handler and George Lopez emerged. Jon Stewart and Stephen Colbert took the news into their own hands.

Late-night TV confronted its biggest identity crisis thanks to streaming television and a highly polarized political landscape.