Image “This is my home. I would feel out of place in L.A.,” said Jimmy Fallon, the new host. Credit... Lloyd Bishop/NBC, via Associated Press

The studio itself is all about its roots. It is the same studio that Johnny Carson starred in before he left for California in May 1972, and that Jack Paar starred in before him. It is also the studio where Mr. Michaels sat in the audience on his own first visit to 30 Rock as a teenager from Toronto, taking in not only Mr. Paar’s show on Christmas Eve, but also the full ambience of Rockefeller Center: the decorated tree, the skating rink and the famous Art Deco lobby of the building that is one of the birthplaces of broadcasting in America. “It was thrilling,” he said.

Like Mr. Michaels, Mr. Fallon, who emerged as a star on “S.N.L.,” has a long association with 30 Rock. Those connections proved a significant factor in the decision to relocate.

“It simply never came up that we would move to L.A.,” Mr. Michaels said. Mr. Fallon, born in Bay Ridge, Brooklyn, and raised upstate in Saugerties, N.Y., said, “This is my home. I would feel out of place in L.A.”

With Mr. Fallon’s “Late Night” show working well, it only seemed logical to move “Tonight” east. Even as television after prime time has become crowded, with stars like Jon Stewart beginning his show at 11 p.m. on Comedy Central and Craig Ferguson ending his show on CBS after 1:30 a.m., the “Tonight” show has retained the top spot in late night. “There’s an old quote attributed to Mr. Bulova,” Mr. Michaels said, referring to the watchmaker. “If it’s ticking, don’t open the back.”