He is largely known for his tenure in the United States House of Representatives, serving twelve terms as a Democrat from 1949 to 1973 from Colorado's Fourth District.

His family had traditionally voted Republican, but the party's in-fighting in 1912 between Theodore Roosevelt and William H. Taft disillusioned Aspinall.

Known as "The Chairman," he led the Interior and Insular Affairs Committee during a period that defined future water and land policy in the United States.

The bill, sponsored by Wayne Aspinall and several western allies, called for damming several areas in the Upper Basin of the Colorado River.

Because the Front Range (Boulder, Denver, Colorado Springs, and Pueblo) had a tremendous population advantage over the Western Slope, most of the state favored the project.

Precedent for this maneuver had been set in 1937 with the Colorado-Big Thompson Project, which transferred Western Slope water to farmers in northeast Colorado.

Aspinall, however, pushed the plan through because he realized that as a strong proponent of public water development, it seemed contradictory for him to block reclamation projects that benefited others.

The bill passed in August 1962 when Aspinall attained a plan calling for the construction of a 28,000 acre-foot (35,000,000 m3) reservoir on the Roaring Fork River near Aspen, which would compensate the Western Slope for its loss of water.

Fry-Ark demonstrated Aspinall's resolve to proliferate the amount of publicly funded water projects throughout the West, pitting him against the wishes of the majority of his constituents in the early 1960s.

One of the first comprehensive pieces of environmental legislation during the era faced a lengthy battle in Congress between Presidents Kennedy and Johnson and western politicians like Aspinall.

Aspinall greatly desired a public land review commission (see below), while one of Kennedy's primary goals was the passage of the Wilderness Act.

Ironically, the National Wildlife Federation named Aspinall their "Conservationist of the Year" in 1964 for his role in the eventual passage of the bill.

Several congressmen, including Arizona senator Carl Hayden, saw this as action as a move that held the state hostage, and many would come to resent Aspinall for it.

Jimmy Carter declared a "Hit List" in 1977 on what he felt was wasteful spending on "pork barrel" water projects, eliminating the other three (among others).

Kennedy's concession in 1963 to enact the Wilderness Act gave Aspinall the go-ahead to organize his pet project, the Public Land Law Review Commission (PLLRC) in 1965.

The Sierra Club accused the study of being "oriented toward maximum immediate commercial exploitation..." predicated upon a world with an "ever-expanding economy and unlimited resources."

Many citizens were also still unhappy with Aspinall for blocking the creation of the Redwood National Park in California for half of the decade until its passage in 1968, and they saw this as more evidence that he served as a mouthpiece for the extractive industries' interests in Congress.

The challenger also accused "The Chairman" of being too connected to the extractive special interests and railed against him for his role in what reformers viewed as a flawed seniority system in Congress.

Aspinall's friend and colleague, Democratic congressman Byron Rogers of Colorado's First District, did not survive 1970's primary season, however.

Merson attacked Aspinall for being slow to recognize developing energy problems, promoting policies that fed constant growth, building needless water projects, and being a tool of special interests.

Merson received extensive external aid, accepting endorsements from The New York Times, Field and Stream, and even Reader's Digest.

Environmental Action, having named Aspinall to their 1972 "Dirty Dozen" list of biggest congressional enemies to the environment, also endorsed Merson.

History credits Aspinall's loss to his age, the strength of the environmental issue in 1972, and the redistricting that cost "The Chairman" much of his conservative support on the Western Slope.

He proudly took part in the Sagebrush Rebellion, a western philosophy popular from 1979–1982 that attempted to reclaim some federally protected land for determination by states and local governments.

Aspinall resumed the practice of law, was a resident of Palisade, Colo., until his death there October 9, 1983; he was cremated, and his ashes were interred at Orchard Mesa Municipal Cemetery, Grand Junction, Colorado.

The United States Post Office and Courthouse in Grand Junction was renamed the Wayne N. Aspinall Federal Building in 1972.