Island No. 1 is a partially submerged island in the Napa River, upstream of San Pablo Bay. It is in Napa and Solano County, California, and parts of it are managed as part of the Napa-Sonoma Marshes W
Island No. 1, submerged in March 2023 (as seen from the northern part of an internal levee, looking south).
An aerial view, looking toward the west, of the Napa River where it flows into San Pablo Bay through Vallejo. Islands visible include, from bottom of image: Mare, No. 1, Knight, Russ, No. 2, Green, Bull, Edgerly, Coon, Little, and Tubbs.