Ryer Island is an island in the Sacramento-San Joaquin River Delta surrounded by Miner Slough and Steamboat Slough at their confluence with the Sacramento River, 6.5 miles north-northeast of Rio Vista. It is in Solano County, California, and managed by Reclamation District 501. The 4,750 ha island is named in honor of a California pioneer, Dr. Washin…Ryer Island is an island in the Sacramento-San Joaquin River Delta surrounded by Miner Slough and Steamboat Slough at their confluence with the Sacramento River, 6.5 miles north-northeast of Rio Vista. It is in Solano County, California, and managed by Reclamation District 501. The 4,750 ha island is named in honor of a California pioneer, Dr. Washington M. Ryer, and his family. A map prepared at the time of statehood shows the area divided by the west fork of the Sacramento River, with the western half identified as Priest Island and the eastern half identified as Sutter Island.