Corvallis (kôrvălˈĭs) [key], city (1990 pop. 44,757), seat of Benton co., NW Oreg., on the Willamette River; inc. 1857. Engineering firms contribute to the city's economy; fruit growing and sawmilling are regional activities. Corvallis is the seat of Oregon State Univ. and the headquarters for Siuslaw National Forest. Nearby are a state forest and a national wildlife refuge.