Interior Secretary Gale Norton resigned Friday from President Bush's Cabinet after five years, FOX News has confirmed.
"There will never be a perfect time to leave," Norton wrote in a two-page resignation letter to President Bush. "There is always more work to do. My leaving now gives you the opportunity to appoint a new secretary to accomplish the goals you set for the rest of your administration."
Norton, who said she will leave in March, became the first woman to lead the department when she was sworn in as the 48th secretary in January of 2001.
President Bush thanked Norton for her service in a statement released by the White House Friday.
"Because of her leadership and thoughtful attention to management, repairs, and maintenance issues, Americans will be able to better enjoy our great national parks and wildlife refuges for generations to come," Bush said.
Norton, who turns 52 on Saturday, led the department as a former Colorado attorney general who promoted the Bush administration's initiative to allow more oil and gas drilling in Western government lands.
"Now I feel it is time for me to leave this mountain you gave me to climb, catch my breath, then set my sights on new goals to achieve in the private sector. Hopefully, my husband and I will end up closer to the mountains we love in the West," Norton wrote in the letter.
During her five-year tenure, Norton worked to open Alaska's Arctic National Wildlife Refuge to oil drilling, eased regulations for quicker approval of drilling permits in New Mexico, Colorado and Wyoming, and helped to pass the Energy Policy Act of 2005 last July.
As Colorado's attorney general from 1991 to 1999, Norton negotiated a $206 billion natural tobacco settlement in a suit by Colorado and 45 other states.
Norton was a protege of James Watt, the controversial interior secretary during President Reagan's first term in office. Watt was forced to resign after characterizing a coal commission in terms that were viewed by some as a slur.
After working for the Agriculture Department for a year, Norton was named an assistant solicitor in the Interior Department in 1985, focusing on conservation and wildlife issues.
Norton lost a bid in 1996 for the Colorado Republican Senate nomination. She later became a co-founder of the Council for Republicans for Environmental Advocacy, which has been linked to disgraced lobbyist Jack Abramoff.
Steven Griles, Norton's former deputy, has also been linked to Abramoff through e-mails that have surfaced, according to members of the Senate Indian Affairs Committee.
Italia Federici, a former Norton associate, helped Abramoff reach Griles in exchange for contributions from the lobbyist's Indian tribe clients, said Sens. John McCain, R-Ariz., and Byron Dorgan, D-N.D.
The Associated Press contributed to this report.