"He has told President Barack Obama that he intends to leave his job by the end of March," the Post says.
Salazar joins other departing members of Obama's first-term team, including Secretary of State Hillary Rodham Clinton, Treasury Secretary Timothy Geithner, Defense Secretary Leon Panetta, and Environmental Protection Agency administrator Lisa Jackson.
From the Post:
"The secretary is not shy talking about how much he loves his job as steward of the country's public lands. He often says the Department of Interior is really the Department of America.
"'As I think about my role as secretary of the Interior, it is perhaps the most wonderful job of any cabinet position in the United States,' Salazar said in December. 'I would not trade it for attorney general or Housing and Urban Development or Transportation because I would find those jobs a little boring.'
"But the pull of family obligations -- he and his wife are primary caretakers of their 5-year-old granddaughter who has autism and is enrolled in a special school -- was too great to commit to four more years, Salazar's office said."