Dirk Arthur Kempthorne (October 29, 1951 – April 24, 2026) was an American politician from the state of Idaho. A Republican, he served as a United States senator from Idaho from 1993 to 1999 and as the 30th governor of Idaho from 1999 to 2006. Kempthorne also served as the 49th U.S. secretary of the interior from 2006 to 2009 under President George W. Bush.
Kempthorne was first elected to public office as mayor of Boise in 1985, where he served for seven years. He served as a co-chair of the Democracy Project at the Bipartisan Policy Center. In November 2010, he was appointed president and CEO of the American Council of Life Insurers.
Born in San Diego on October 29, 1951, and raised in San Bernardino, California, Kempthorne graduated from San Gorgonio High School in San Bernardino. He attended San Bernardino Valley College, then transferred north to the University of Idaho in Moscow, from which he graduated in 1975 with a degree in political science, and served a term as student body president. Upon graduation Kempthorne served as an assistant to the director of the Idaho Department of Lands and then as executive vice president of the Idaho Home Builders Association.
In 1982, Kempthorne managed the gubernatorial campaign for Lieutenant Governor Phil Batt, who lost to the incumbent Democrat, Governor John V. Evans. In 1983 Kempthorne became state public affairs manager for FMC Corporation.
Kempthorne and his wife, Patricia Kempthorne, also a UI graduate, had two adult children, Heather and Jeff.
On March 31, 2025, Kempthorne announced that he had been diagnosed with colon cancer and would begin chemotherapy. He died in Boise on April 24, 2026, at the age of 74.
Kempthorne's first major political victory came at age thirty-four, when he was elected mayor of Boise in 1985. As mayor, Kempthorne became very popular and was unopposed for reelection in 1989.
In 1992, U.S. Senator Steve Symms decided not to seek a third term and Kempthorne pursued the Republican nomination for the seat. In the general election, Kempthorne defeated Democratic congressman Richard H. Stallings.
In the Senate, Kempthorne sponsored and helped pass the Unfunded Mandates Reform Act of 1995, a bill meant to prohibit Congress from imposing unfunded federal mandates on states. The bill aimed to:
[C]urb the practice of imposing unfunded Federal mandates on States and local governments; to strengthen the partnership between the Federal Government and State, local and tribal governments; to end the imposition, in the absence of full consideration by Congress, of Federal mandates on State, local, and tribal governments without adequate funding, in a manner that may displace other essential governmental priorities; and to ensure that the Federal Government pays the costs incurred by those governments in complying with certain requirements under Federal statutes and regulations, and for other purposes.
Also in 1995, Senator Kempthorne introduced amendments to the Safe Drinking Water Act. This bill was signed into law by President Bill Clinton on August 6, 1996.
During his six years in the Senate, Kempthorne scored a "0" on the League of Conservation Voters' legislative scorecards every year except 1993, when he scored 6 percent on the basis of one vote against funding a rocket booster for the space program that environmentalists judged harmful to the environment. His overall LCV score for that period was less than 1%.
Kempthorne was expected to run for reelection in 1998, but instead decided to run for the open seat for governor. The incumbent, Phil Batt, shocked the state by announcing his retirement after only one term in office, citing his age (71) as the prime factor in his decision. Kempthorne's Senate seat would be won by Republican congressman Mike Crapo of Idaho Falls.
Kempthorne won the gubernatorial election in a landslide, receiving 68 percent of the vote while his Democratic opponent, Robert C. Huntley, received only 29 percent. He was reelected in 2002 with 56 percent of the vote; his Democratic opponent, Jerry Brady, polled 42 percent. Kempthorne's campaign spent nearly $200,000 more than it had received in contributions prior to the election. Subsequently, he spent the next two years raising funds to pay off the campaign debt.
U.S. Secretary of the Interior
On March 16, 2006, Kempthorne was nominated by President George W. Bush to replace Gale Norton and become the 49th United States Secretary of the Interior. On May 10, 2006, Kempthorne's nomination was approved by voice vote by the United States Senate Committee on Energy and Natural Resources. He was confirmed by the full Senate on May 26 and resigned as Idaho Governor to accept the position the same day. Lieutenant Governor Jim Risch succeeded Kempthorne as Idaho Governor, filling out the remaining months of his term.
Upon Kempthorne's appointment as Secretary of the Interior, environmental groups characterized him as someone who has "almost always favored changing laws like the Endangered Species Act and the Safe Drinking Water Act to make them more favorable to commercial interests."
As Secretary of the Interior, Kempthorne was criticized for not placing any plants or animals on the U.S. Federal Endangered Species list from the time of his confirmation on May 26, 2006. As of September 2007, Kempthorne held the record for protecting fewer species over his tenure than any Interior Secretary in United States history, a record previously held by James G. Watt for over 20 years.