Keizer (IPA: /ˈkɑɪzɚ/) is a city in Marion County, Oregon, Unite States. It was named for Thomas Dove and J.B. Keizur, two pioneers who arrived in the Wagon Train of 1843, and later filed donation land claims. The population was 32,203 at the 2000 census. The 2006 estimate is 34,880 residents.