From Wikipedia:
The program has typically consisted of live video of Dick Clark in Times Square in New York City, counting down until the New Year ball comes down. Since 2005, Ryan Seacrest has been hosting the show outdoors at Times Square while Dick Clark offers comments from a studio. After the ball drops, the focus of the program switches to pre-taped musical segments taped in Hollywood (December 31, 1972-December 31, 1998; December 31, 2000-December 31, 2008) or Las Vegas (December 31, 2009). The segments from Times Square are broadcast live in the Eastern Standard Time zone, and it is delayed for the other time zones so that they can ring in the new year with Clark when midnight strikes in their area.
It first aired on NBC in 1972 and 1973, then it moved to ABC in 1974 and has aired there every year since, except on New Year's Eve 1999 into New Year's Day of 2000. In the three and a half decades it has been on the air, the show has become a mainstay in American New Year's celebrations. Watching the ball drop on Clark's show is considered an annual cultural tradition for the New Year's holiday.
Since Sunday, December 31, 2000, a pre-show, Dick Clark's Primetime New Year's Rockin' Eve has aired live from 10:00 p.m. to 11:00 p.m. The hour-long program features live reports on the festivities in Times Square, as well as various performances. From 11:00 to 11:35 p.m. ET/PT, the show pauses for local newscasts from ABC's affiliates (stations in Central and Mountain Time Zones may have additional local programming before the show resumes at 11:30 p.m. local time). Despite the name, Dick Clark has not actually appeared in the prime time show since 2003.
Before Dick Clark, the best-known New Year's Eve shows on radio and then television were hosted by bandleader Guy Lombardo, who hosted 21 consecutive New Year's Eve shows from 1956 to 1976 on CBS, and for a time in syndication. Lombardo's first radio broadcast on New Year's Eve was heard on December 31, 1928 over CBS Radio, and for a time he even split hosting duties by broadcasting on CBS Radio before 12 Midnight EST and on NBC Radio after Midnight. Lombardo would host 48 straight New Year's Eve broadcasts until his death in 1977, and famously performed "Auld Lang Syne" by his Royal Canadians as the clock struck 12 Midnight, ushering in the start of a New Year.
Once the Lombardo orchestra began their annual television shows, there would be a live segment from Times Square, which was (and still is) the focal point of the nation's largest New Year's celebration. In the early years of Lombardo's television specials, Robert Trout reported on and counted down to Midnight in New York's Times Square; but for most of Lombardo's years on television, another legendary newsman, Ben Grauer, had the honor. (Grauer, by the way, also reported from Times Square for NBC Radio on celebrations following the surrender of Japan on August 14, 1945.
The first New Year's Eve special on television was broadcast on December 31, 1941 on WNBT New York, and consisted of entertainment broadcast from the Rainbow Room, atop the RCA Building in New York's Rockefeller Center.[3]
Due to World War II, there would be no more New Year's Eve specials on television until December 31, 1945. WNBT produced a remote broadcast of festivities in Times Square. While NBC had begun to feed programs to WRGB is the Albany area and WPTZ in Philadelphia, information is unavailable as to whether either or both of these stations broadcast the program, or if it was seen just locally in New York.[4]
Unless New Year's Eve fell on a weekend, NBC would carry a special New Year's version of "The Tonight Show" each year beginning in 1954, including coverage of the arrival of the New Year in Times Square.
Dick Clark himself had actually emceed one New Year's Eve TV special prior to 1972; on December 31, 1959, he emceed a 90-minute New Year's special on ABC. One of the guests was Frankie Avalon. But it would be the last time Clark would do a New Year's Eve television special for the next thirteen years.
By the 1970s, Lombardo's big band music skewed to an older generation, so Dick Clark started his telecast in 1972 to compete.
The first show, Three Dog Night's Year's Rockin' Eve 1973, on NBC, was hosted by Three Dog Night and also featured Blood, Sweat & Tears, Helen Reddy and Al Green.