When former Gov. Walter J. Hickel of Alaska became President Richard M. Nixon’s Interior secretary, Mr. Watt was named a deputy with oversight for water and power resources. In 1975, President Gerald R. Ford named him to the Federal Power Commission. He became a proponent of the “Sagebrush Rebellion,” a Western movement that sought regional control of public resources.

In 1977, Mr. Watt became president and chief counsel of the Mountain States Legal Foundation, created by the Colorado brewer Joseph Coors to protect property rights. He filed many lawsuits to challenge Interior Department environmental policies.

He and Reagan knew his nomination for Interior secretary would provoke opposition because of his anti-environment, pro-development activities. But he was easily confirmed by the Senate after insisting that controlled development of resources would strengthen the nation in an energy emergency.

After leaving the government, Mr. Watt was a lobbyist for builders seeking contracts from the Department of Housing and Urban Development from 1984 to 1986. In 1995, he was charged with 25 counts of perjury and obstructing justice by a federal grand jury investigating fraud and influence-peddling during his lobbying at HUD. But the prosecution’s case deteriorated, the felony charges were dropped and he pleaded guilty to a single misdemeanor and was sentenced to a $5,000 fine and 500 hours of community service.

Mr. Watt, who had a home in Jackson Hole, Wyo., and in recent years lived in Wickenburg, Ariz., co-wrote “The Courage of a Conservative” (1985, with Doug Weed), about conservative political agendas.

In 2001, when the administration of George W. Bush proposed drilling for oil on public lands in an effort to cope with the nation’s energy problems, Mr. Watt hailed the approach being advanced by Vice President Dick Cheney. “Everything Cheney’s saying, everything the president is saying, is exactly what we were saying 20 years ago,” he told The Denver Post. “Twenty years later, it sounds like they’ve just dusted off the old work.”

Eduardo Medina contributed reporting.