On November 8, 1994, Koster won the election and became a Republican member of Washington House of Representatives for District 39, Position 2. Koster defeated Hans Dunshee with 52.70% of the votes. Koster's term began on January 3, 1995.[3][unreliable source?] On November 5, 1996, as an incumbent, Koster won the election and continued serving District 39, Position 2. Koster defeated Jeff Soth with 52.78% of the votes.[4][unreliable source?] On November 3, 1998, as an incumbent, Koster won the election and continued serving District 39, Position 2. Koster defeated Patricia Patterson with 51.87% of the votes.[5][6][unreliable source?]
On November 6, 2001, Koster was elected to the Snohomish County Council, District 1. Koster defeated incumbent Democrat Mike Ashley and others with 51.65% of the votes.[7][unreliable source?] As an incumbent, Koster was reelected in November 2005 and November 2009, representing Council District 1.
Koster has three times ran unsuccessfully for the United States House of Representatives in 2000, 2010, and 2012. In November 2015, Koster was elected Charter Review Commissioner for Snohomish County.[8]
On December 20, 2013 it was announced that the term-limited Koster would be the first-ever Snohomish County Ombudsman after his term in the Snohomish County Council ended on January 1, 2014.[9]
^Walsh, Kylie (July 25, 2017). "Representative John Koster to step down". Washington State Wire. Archived from the original on April 3, 2019. Retrieved September 2, 2021.{{cite web}}: CS1 maint: bot: original URL status unknown (link)()