Yamhill County is one of the 36 counties in the U.S. state of Oregon. As of the 2020 census, the population was 107,722. The county seat is McMinnville. Yamhill County was named after the Yamhelas, members of the Kalapuya Tribe. Yamhill County is part of the Portland-Vancouver-Hillsboro, OR-WA Metropolitan Statistical Area. It is in the Willamette Valley.