Santa Rosa Island is the second largest of the Channel Islands of California at 53,195 acres (215.27 km² or 83.118 sq mi). Defined by the United States Census Bureau as Block 3009, Block Group 3, Census Tract 29.10 of Santa Barbara County, California. It is part of Channel Islands National Park. Highest peak is Vail Peak, at 1,589 feet (484 m).