Washington's 1st congressional district

The district from 2003 to 2013

Prior to the 2012 redistricting, the district encompassed part of Northwest Seattle and largely suburban areas north and east of Seattle, including Shoreline, Edmonds, Lynnwood, Mountlake Terrace, Kenmore, Bothell, Kirkland, and Redmond, as well as Bainbridge Island and part of the Kitsap Peninsula. Until March 20, 2012, it was represented by Democrat Jay Inslee from Bainbridge Island. Inslee resigned to focus on his run for Governor of the state;[3] the seat remained vacant until the special election that coincided with the November 2012 general election.[4][5]

The former House seat of powerful U.S. Senator Warren G. Magnuson, the district was a swing district throughout much of the 1990s, changing hands and parties three times in four elections. Before the election of future U.S. Senator Maria Cantwell in 1992, the district had been in Republican hands for 40 years (and 42 of the previous 46 years). Since the 1998 election, when Inslee was first elected, the growing Democratic trend in the Seattle area enabled him to turn it into a fairly safe seat. He had been re-elected six times, with little difficulty, most recently in 2010.

The district from 2013 to 2023

The 2012 redistricting drastically changed the 1st district. Much of this area was previously part of the 2nd district, but in the new map, the 2nd has shrunk significantly. Jay Inslee (D) was the representative of the 1st district until resigning to run for governor of the state, but most of the district has been represented by Rick Larsen (D), of the 2nd district, in the past.

Soon after the 2012 general election polls closed, the Seattle Times and national news organizations called the district for Democrat Suzan DelBene, defeating Republican John Koster with a margin that the Seattle Times called "unexpectedly decisive",[6] reflecting the difficulty of predicting the vote in the new district. The certified results confirmed her significant margin.[7] DelBene also won the election for the remainder of Inslee's term in the old first district, and after being sworn in on November 13, 2012.