WASHINGTON - Interior Secretary Ryan Zinke is leaving next year, President Donald Trump announced Saturday – the latest high-level departure from the president's administration.

Zinke has held his position since the start of Trump's presidency, making him one of a handful of Cabinet members who still have their original post within the administration.

The former Navy SEAL wielded an unflinching demeanor as the head of a sprawling agency. Interior has roughly 70,000 employees, manages the country's natural resources on land and offshore, and oversees federal lands that collectively make up a fifth of the country.

For much of his tenure, Zinke, 57, a former Montana congressman, was the target of allegations and investigations. Those were sure to be examined in public in the new Democrat-led House of Representatives.

Here are some of the key controversies in Zinke's time as President Donald Trump's Interior Secretary.

A land development deal

Zinke came under scrutiny for his role in a Montana land deal that could benefit him personally. The Interior Department's own inspector general reportedly referred this case to the Department of Justice for potential prosecution.

The investigation examined a meeting Zinke had with David Lesar, chairman of Halliburton, an energy company. At issue: a project near land owned by Zinke's family foundation. The project, according to CNN, could improve the value of the Zinke land.

Zinke said that meeting was innocent, and the pair just talked about the background of the project.

"We go out to dinner. We talk about the background of the park: what are the neighbors like, what was the vision of the park, where the boundaries are, where the water table is because the water table has changed over time, what the railroad is. So they have the background," Zinke said in June, during an interview with a Montana radio show.

Shrinking national parks

Zinke also faced questions and scrutiny over his rationale for shrinking national parks and monuments.

He was criticized heavily by environmental groups. His cuts to the size of parks engineered "the largest rollback of public land protection in American history," said Kieran Suckling, executive director of the Center for Biological Diversity, an environmental group.

The Interior's inspector general investigated the shrinking of one specific park, the Grand Staircase-Escalante National Monument in Utah. The watchdog group examined whether Zinke redrew the lines of the park to help a former Utah lawmaker, a Republican and supporter of the Trump administration.

Last year, the president approved Zinke's recommendation to cut the monument by nearly half. The new boundaries helped free land surrounding 40 acres owned by former state Rep. Mike Noel and, according to the Washington Post, would help bring a proposed water pipeline to the area.

The agency's watchdog released its findings last month, saying it found "no evidence" that Zinke altered the monument to help Noel or that Zinke and his staff even knew of the former lawmaker's financial interest in the changes.

Casino deal

The Interior Department's watchdog group was also examining why Zinke denied a casino deal in Connecticut with the Mashantucket Pequot and Mohegan tribes when staffers at Interior recommended approving it, the Washington Post reported.

The new casino would have been a competitor with MGM Resorts. The company and several senators lobbied for Zinke to deny a permit for the project, which he did.

Travel concerns

The agency's inspector general admonished Zinke for his use of military charter planes. One trip, in June 2017, cost $12,375 for a trip to speak at the developmental camp for the Golden Knights, a professional hockey team based in Las Vegas.

He also was criticized by lawmakers for spending more than $53,000 on three helicopter trips in 2017, including one that returned him to Washington in time to take a horseback ride with Vice President Mike Pence, according to The Associated Press.

Office remodeling

Zinke drew criticism earlier this year for moving forward with the replacement of three sets of doors at Interior's historic headquarters, costing nearly $139,000.

A spokeswoman for Zinke said at the time he was unaware of the contract before reporters started asking about it.

The work is part of a decade-long modernization of the 1936 building that began before Zinke took office in March 2017.

More:Interior Secretary Ryan Zinke accused of mixing politics with government business

Offshore drilling exemption for Florida

Zinke made a big deal in January when, after the president unveiled his plan to open up 90 percent of the Outer Continental Shelf off the U.S. coast to oil and gas exploration, he flew to Florida and revealed the Sunshine State would be exempt from offshore drilling.

It was seen as a political gambit and a huge gift to Florida Gov. Rick Scott, who weeks later decided to challenge Sen. Bill Nelson, D-Fla.

But the Washington Post later reported the move caused some friction within the White House because it was not coordinated with the West Wing's political shop.

Contributing: Ledyard King, Associated Press