Trentwood is a census-designated place in Spokane County, Washington, United States. The population was 4,388 at the 2000 census. As of 2003, the Trentwood area forms the northernmost portion of the City of Spokane Valley. Trentwood apartments for rent comparison page shows most up to date rent information on Trentwood apartments and houses. Rent information is obtained from multiple rental sources but we cannot guarantee their accuracy.