Democratic Rep. Henry Waxman to retire

CNBC.com with AP

Democratic Rep. Henry A. Waxman, who during his four decades in Congress pushed for legislation on clean air, Obamacare and expansion of Medicaid, announced plans Thursday to retire at the end of the year.

Waxman, 74, was elected to represent his California district in 1974 in the aftermath of Watergate. During his 20 terms, he pushed for investigations into the tobacco industry and was instrumental in getting President Barack Obama's health-care overhaul completed.

Rep. Henry Waxman in July 2013.
Julia Schmalz | Bloomberg | Getty Images

"I first ran for office because I believe government can be a force for good in people's lives," Waxman said in a statement announcing his retirement plans. "I have held this view throughout my career in Congress. And I will leave the House of Representatives with my conviction intact. I have learned that progress is not always easy. It can take years of dedication and struggle. But it's worth fighting for."

There are currently 233 Republicans and 200 Democrats in the House.

—By CNBC.com. AP contributed to this story.