Bouldin Island is an island in the Sacramento-San Joaquin River Delta in San Joaquin County, California, 20 kilometers (12 mi) northwest of Stockton. The 2,400 ha (5,900-acre) island is bounded to the north by South Mokelumne River which separates the island from Staten Island. To the east, the island is bounded by Little Potato Slough, to the south by Potato Slough, and to the west by the Mokelumne River. The State Route 12 crosses the northern section of Bouldin Island, which is also called Kettleman Lane on the island. A swing bridge over the Mokelumne River on SR 12 connects the northwestern part of the island to Andrus Island.