Interior Secretary Ken Salazar said today he'll step down from his Cabinet post by the end of March and return to his home state of Colorado.

Obama lauded Salazar, saying that as secretary he had "helped usher in a new era of conservation for our nation's land, water, and wildlife.

"I have valued Ken’s friendship since we both entered the Senate in 2005, and I look forward to receiving his counsel even after he returns to his home state of Colorado," Obama said.

The White House was mum about a successor, but among those said to be in the running for his post: Washington Gov. Chris Gregoire, who leaves office this month. Gregoire in a November interview played down the possibility of the new job.

"I really haven't had much time," she said. "I've been working on the campaign. I've been working on a budget that I've got to get out. And I'm a brand-new, first-time grandma of just a couple few days…I haven't had any time to think about it."