Bouldin Island, an island located in Northern California, is bounded to the north by the South Mokelumne River which connects the island to the adjacent sea.
Bouldin Island is an island in the Sacramento-San Joaquin River Delta in San Joaquin County, California, 20 kilometers (12 mi) northwest of Stockton on the Stockton Deepwater Shipping Channel. The 2,400 ha (5,900-acre) island is bounded to the north by South Mokelumne River which separates the island from Staten Island. A swing bridge over the Mokelumne River on SR 12 connects the northwestern part of the island to Andrus Island. Sacramento-San Joaquin River Delta The river flows west from a rugged portion of the central Sierra Nevada into the Central Valley and ultimately the SacramentoSan Joaquin River Delta, where it empties into the San Joaquin River-Stockton Deepwater Shipping Channel. The Stockton Deepwater Shipping Channel is part of the vast SacramentoSan Joaquin River Delta that has a connection to the Pacific Ocean. 
