LOS ANGELES — Enter the world of "Mad Men" and you're stepping into the past.

Whether you turn on the television when the second season begins (Sunday, 8, 9 and 11 p.m., AMC) or step onto the set in downtown Los Angeles, it feels as if you've gone through a time warp that carried you back to the early 1960s. The era is meticulously — almost obsessively — re-created in a show that's the absolute darling of the critics.

It won three of 11 Television Critics Association awards last week, including best new program, best drama and program of the year.

"Mad Men" follows the staff at the Sterling Cooper advertising agency — a top New York firm. (The title refers to what Madison Avenue ad men called themselves.) As we learned in the first season, despite the apparently straight-laced nature of the time and the characters, all is not what it seems.

You need look no further than creative director Don Draper (Jon Hamm), who isn't even "who" he pretends to be, let alone "what" he pretends to be. And the series is populated with indelible characters, including agency chief Roger Sterling (John Slattery); incredibly creepy young upstart Pete Campbell (Vincent Kartheiser); junior copywriter Peggy Olson (Elisabeth Moss); office manager Joan Holloway (Christina Hendricks); Don's troubled wife, Betty (January Jones); and closeted art director Salvatore Romano (Bryan Batt).

Where all this came from — the show, the setting, the return to 1960 — even the show's creator/executive producer/writer can't quite say.

"I mean, the creative process is mysterious," said Matt Weiner. "I had an obsession. I've been asked that question, and I don't have a good answer for it."

He did, however, point to the early 1960 as "a golden age for the United States. ... There really was just this magnanimous spirit about the world, a cultural openness. I know it's seen as a repressed period, but it's really a culturally very open period. A lot of freedom and a lot of the ideas that we associate with the '60s were born in that period, and I was interested in those "environmentalism, attitudes toward materialism, Bohemianism, art, plays.

"And then a lot of it's personal. You know I just sort of identified with that and identified with sort of the dichotomy between the way we are on the outside and the way we're perceived."

He also used the word "obsessive" to describe his focus on making sure the look of the show is right. Everything you see, whether it's what the actors or wearing, where they live or wear, they work, is actually of the period of a re-creation.