Wallop died at his ranch home near the community of Big Horn in northern Wyoming, said Kerrie Kimmel of the Kane Funeral Home in Cheyenne. He had been ill for several years, according to family friend Bruce McCormack, publisher of the Cody Enterprise.
"He was part of a remarkable Wyoming congressional delegation back in the 1980s, along with Dick Cheney and Al Simpson; the three of them were just remarkably powerful and effective," McCormack said. "It was unlike hardly any state. To have a delegation of that strength was just a real advantage to Wyoming."
Wallop gained a significant victory when President Reagan began pushing a space-based anti-missile defense concept. Wallop was among a group of conservatives who had espoused the plan for years before Reagan came to support it.
His 18 years in the Senate included time as the ranking Republican on the Energy and Natural Resources and Armed Services committees.
Key legislation Wallop helped pass included an energy bill in 1992 and major portions of Reagan's tax cuts in 1981. In 1984, Wallop helped create the Wallop-Breaux Trust Fund, an account used to finance state fisheries and boating programs. The fund uses money raised through special fees and taxes on fishing gear and motorboat fuels.
Wallop didn't seek reelection in 1994 but remained active politically as director of the conservative Frontiers of Freedom Foundation think tank.
Wallop was born Feb. 27, 1933, in New York City — his rancher parents were there for only a brief time — and attended Cate School in Carpinteria. He graduated from Yale in 1954. After serving in the U.S. Army from 1954 to 1957, he returned to Wyoming to ranch.
He served two terms in the Wyoming House, from 1969 to 1972, and one term in the Wyoming Senate, from 1973 to 1976. He ran for Wyoming governor in 1974, losing in the Republican primary.
His Senate tenure included several prominent assignments. He was chairman of the Select Committee On Ethics from 1981 to 1983 during the trial of New Jersey Democrat Harrison A. Williams Jr. on Abscam bribery charges. Wallop was the first non-lawyer to serve on the Judiciary Committee.
He is survived by his fourth wife, Isabel, and four children.