Hillsboro is a city in the U.S. state of Oregon and is the county seat of Washington County. Situated in the Tualatin Valley on the west side of the Portland metropolitan area, the city hosts many high-technology companies, such as Intel, locally known as the Silicon Forest. The population was 106,447 at the 2020 census, making Hillsboro the fifth-most populous city in Oregon. Settlers founded a community here in 1842, later named after David Hill, an Oregon politician.