For years, CBS & ABC fought a losing battle for late night ratings against NBC's Tonight Show, especially during the Johnny Carson era (1962-92). Each network had tried their own talk shows. CBS recruited Merv Griffin, who soon found out his show was better suited to earlier hours, and, near the end of the Carson era, Wheel of Fortune MC Pat Sajak, whose short-lived talk show was previously reviewed. ABC tried out Joey Bishop, but had more success with Dick Cavett.
Unable to resist the temptation of trying again, ABC, in January 1973, began a late night checkerboard format under the title, ABC's Wide World of Entertainment, which included new Cavett interviews, plus comedy specials and other various items, including, beginning in 1974, reruns of primetime series, either their own, or acquired from other networks.
Unfortunately, the checkerboard format didn't work after all, and the block was laid to rest after 3 years, with ABC opting to stick with the reruns under the new title, ABC Late Night, though that wouldn't survive the decade, either.
Curiously, game show mogul Mark Goodson chose ABC, rather than CBS, and Wide World of Entertainment, for a 25th anniversary salute to What's My Line?, largely because its original moderator, John Daly, was moonlighting from his day job as a news anchor for----wait for it---ABC. What's My Line? At 25, with Goodson, Daly, & Arlene Francis, aired in May 1975.
Back in those days, of course, ye scribe couldn't stay up that late, so there's no rating.