In 1974 Williams ran an unsuccessful primary election campaign against future Senator Max Baucus for the Democratic Party nomination for Montana's U.S. House 1st District Representative.

That November, Williams defeated Republican Jim Waltermire in one of Montana's largest door-to-door campaigns, winning 57% of the vote and gaining election to the 96th U.S. Congress.

[2] Nearly a year later, in July 1988, the University of Pennsylvania's Institute of Contemporary Art (ICA) received an NEA grant and used it to fund a retrospective exhibition of Robert Mapplethorpe's work which included some graphic sexual imagery.

Pat Robertson took out a full-page newspaper advertisement addressed to members of Congress, which read: "Do you also want to face the voters with the charge that you are wasting their hard earned money to promote sodomy, child pornography and attacks on Jesus Christ?...

[6] Aware of the NEA's desperate situation, and the impossibility of pulling together a core of support for a straight, five-year reauthorization, Representative Williams worked throughout the summer to formulate a compromise bill.

During the House-Senate conference on the Interior appropriations bill, the Williams-Coleman language prevailed over the amendments from Helms and Orrin Hatch (R–UT), and subsequently became law.

"[9] In 1980 Williams won reelection against Jack McDonald with 61% of the vote; in 1982 against Bob Davies with 60%; in 1984 against Gary Carlson with 67%; in 1986 against Don Allen with 62%, 1988 against Jim Fenlason with 61%; in 1990 against Brad Johnson.

In 1992 Montana lost its second seat in the U.S. House of Representatives, leaving Williams to campaign against fellow incumbent Ron Marlenee.

He chose not to run for reelection in 1996, and Republican Rick Hill defeated Bill Yellowtail to become Montana's new U.S. Representative that year.

Williams was on the board of directors of the Student Loan Marketing Association, the now-disbanded GSE subsidiary of U.S.A. Education (Sallie Mae).

[11] Nominated for a seat on the Montana Board of Regents of Higher Education in 2012 by then-governor Brian Schweitzer, Williams endured opposition to his pending confirmation.

It arose due to publication of an out-of-context statement made to a New York Times reporter regarding half-a-dozen players on the University of Montana football team who had recently run afoul of the law.