what county is portland or in?
Homefacts City Report. Portland is located in Multnomah County, OR. The population is 603,650, making Portland the largest city in Multnomah County and the largest city in the state of Oregon. There are 169 public schools in Portland with an average Homefacts rating of B. The total crime rate for Portland is moderate, and there are 204 registered sex offenders residing in the city.