"We have established an enduring vision for conservation in the 21st century that recognizes all people from all walks of life," Salazar said in a statement. "We have undertaken the most aggressive oil and gas safety and reform agenda in U.S. history, raising the bar on offshore drilling safety, practices and technology and ensuring that energy development is done in the right way and in the right places."
For some critics, his departure is long overdue.
"Secretary Salazar was not a friend to my home state of Utah or other public lands states for that matter," said GOP Rep. Rob Bishop, chairman of the House subcommittee over national parks and public lands who has often butted heads with Salazar.
"Under his watch," Bishop added, "the Department of Interior sought to impose historic new limits on access and multiple use of our nation's resources and worked aggressively to hinder certain types of domestic energy production."
One of Salazar's first moves came days into President Barack Obama's administration when the Interior secretary shelved 77 oil and gas leases, setting off a firestorm from energy industry advocates. Rumors of potential new national monuments which never materialized as well as a slowdown on oil shale exploration further deepened the angst with many Utah politicians.
After the state balked at a proposed "wild lands" policy that could have blocked off parts of the state from development without congressional approval of the formal wilderness designation, Salazar eventually said he wouldn't follow through on that plan.
The department, though, did approve two Uinta Basin natural-gas drilling sites that added thousands of new wells and a potash plant in southern Utah expected to create hundreds of jobs. Utah at last report had some 11,000 producing wells an all-time high for the state. At the same time, Salazar attempted to bring various sides of the public lands debate together with listening tours across the nation.
"Secretary Salazar has shown much-needed leadership for conservation at the Department of the Interior, including the opportunities to protect our wild places through the America's Great Outdoors Initiative, his efforts to restore balance to a broken oil-and-gas-leasing program, and his creation of a program to advance clean, renewable energy on public lands," said Wilderness Society President Jamie Williams.
Utah Petroleum Association President Lee Peacock gave a less-enthusiastic review.
"We haven't agreed with many of the policies and initiatives out of the department," he said, "but we continue to look forward to work together to further the goal of national energy security and developing responsibly the vast resources in Utah and other public-lands states."
Whoever fills Salazar's spot will face many challenges, chief among them finding common ground between the interests of producing energy from public lands and protecting them for future generations.
"My hope is that the next Department of Interior secretary is a fellow Westerner," Bishop said. "It is equally important that whoever assumes the helm of the Interior recognizes the importance of multiple use and access and is willing to stand up to special-interest groups looking to the administration to impose restrictive new policies through executive fiat."
The possible list of replacements includes several Westerners: Rep. Raul Grijalva, an Arizona Democrat who has pressed for more wilderness protection; former Rep. Norm Dicks, a Washington Democrat who has won applause from the Wilderness Society; former Washington Gov. Christine Gregoire; former North Dakota Sen. Byron Dorgan; and former Montana Gov. Brian Schweitzer as well as ex-Wyoming Gov. Dave Freudenthal.
The nominee is likely to face tough questions from Western members of Congress. For example, then-Sen. Bob Bennett, R-Utah, held up the nominations of many of Salazar's top deputies over the oil-and-gas-lease issue.
Sen. Orrin Hatch, R-Utah, sparred with Salazar on many occasions but the senator said Salazar was at least willing to have a conversation when the two didn't agree. Still, the senator says Interior's past actions don't hint at a positive future for advocates of energy exploration.
"Westerners have always been forced to stand up to Washington on issues like land rights, endangered species and energy production," Hatch said. "And sadly that's continued to be the case for the past four years."
Salt Lake City lawyer Pat Shea, who led the Bureau of Land Management under President Bill Clinton, praised Salazar for his understanding of Western issues but was disappointed that the secretary didn't lead out more on controversies that affected Utah.
Shea, one of the attorneys for convicted monkey-wrencher Tim DeChristopher, said Interior under Salazar was too soft on energy developers whose misconduct has caused real damage to the land in contrast to DeChristopher's crime of disrupting a sale of leases that later proved invalid.
Rep. Jim Matheson, D-Utah, noted that canceling those leases so early in the administration got Interior off to a bad start with Utahns, but Salazar did help out the state with the Uinta Basin natural-gas well approvals.
"I will acknowledge that the department did move forward on some of those things," Matheson said, "but, in general, we've not agreed on things."
Still, without any evidence of a shift at Interior, Matheson doesn't envision its approach to public lands or energy will change.
"I don't see a significant change in policy, whoever happens to take the position, to be honest."
Brian Maffly contributed to this story.
Utah Gov. Gary Herbert statement on Salazar
"I have high regard for Ken Salazar and have a good personal relationship with him. He is truly a stand-up guy. In spite of some of our understandable differences on policy, we worked diligently to find common ground and a positive outcome; our mutual focus was to optimize our public land. I wish him all the best as he returns to Colorado."