Multnomah County is one of 36 counties in the U.S. state of Oregon. It is part of the Portland metropolitan area and though smallest in area, it is the most populous county. Its county seat, Portland, is the state's largest city. As of the 2010 census, the county's population was 735,334.
Multnomah County (the thirteenth in Oregon Territory) was created on December 22, 1854, formed out of the eastern part of Washington and the northern part of Clackamas counties. Its creation was a result of a petition earlier that year by businessmen in Portland complaining of the inconvenient location of the Washington County seat in Hillsboro and of the share of Portland tax revenues leaving the city to support Washington County farmers. County commissioners met for the first time on January 17, 1855. The county was likely named after Native American people first recorded in the journals of the Lewis and Clark Expedition, Mulknomans, who lived in a village on the east side of present-day Sauvie Island; an alternative theory holds that Multnomah is a corruption of nematlnomaq, meaning down river.
In 1924, the county's three commissioners were indicted and recalled by voters "in response to 'gross irregularities' in the award of contracts for construction of the Burnside and Ross Island bridges"; since all three had been supported by the Ku Klux Klan, their recall also helped reduce that organization's influence in the city.
In 1968, the Oregon Legislative Assembly referred a bill, Ballot Measure 5, to voters that would amend the state constitution to allow for consolidated city-county governments when the population is over 300,000. The 1968 voters' pamphlet noted that Multnomah County would be the only county in Oregon affected by the measure and voters approved the referendum in the 1968 general election. Since the approval of Measure 5 in 1968, an initiative to merge the county with Portland has been considered and placed on the county ballot several times. The merger would have formed a consolidated city-county government like that of San Francisco, California. None of these proposals has been approved.
In the 2000 presidential election, Multnomah played a decisive role in determining the winner of the state's electoral votes. Al Gore carried the county by more than 104,000 votes, enough to offset the nearly 100,000-vote advantage that George W. Bush had earned among Oregon's 35 other counties. The Democratic tilt was repeated in 2004, when John Kerry won by 181,000 votes, and in 2008 when Barack Obama won by 204,000 votes.
In February 2001, the Multnomah County Board of Commissioners unanimously accepted the recommendation of the Library Advisory Board and authorized the library to enter into a lawsuit to stop the Children's Internet Protection Act. The US Supreme Court ultimately decided in 2003 that the law was constitutional in US v. ALA. However, the library chose to turn down $104,000 per year of federal funding under CIPA to be able to continue to offer unfiltered Internet access.
Faced with decreasing government revenues due to a recession in the local economy, voters approved a three-year local income tax (Measure 26-48) on May 20, 2003 to prevent further cuts in schools, police protection, and social services. Multnomah County was one of the few local governments in Oregon to approve such a tax increase.
On March 2, 2004, Multnomah County Chair Linn announced the county would begin granting licenses for same-sex marriages, pursuant to a legal opinion issued by its attorney deeming such marriages lawful under Oregon law. Her announcement was supported by three other commissioners (Serena Cruz, Lisa Naito & Maria Rojo de Steffey), but criticized by Lonnie Roberts, who represents the eastern part of Multnomah county and was left out of the decision. Within a few days, several groups joined to file a lawsuit to halt the county's action; see Same-sex unions in Oregon.