Oregon's 3rd congressional district covers most of Multnomah County, including Gresham, Troutdale, and most of Portland east of the Willamette River (parts of Northwest and Southwest Portland lie in the 1st and 5th districts).

With a Cook Partisan Voting Index rating of D+22, it is the most Democratic district in Oregon and the third most Democratic district in the Pacific Northwest.

Sources (official results only): A special election was held on May 21, 1996 to fill the vacancy created when incumbent Ron Wyden resigned effective February 5, 1996 after winning a special election to the United States Senate.

The winner of the election, Earl Blumenauer, served the remainder of Wyden's two-year term.

Before the 2002 redistricting, the whole of Multnomah County was included in the district; it lost southwest Portland to the 1st and 5th districts, but it gained most of its current portion of Clackamas County.