Stone Lakes National Wildlife Refuge (Refuge) was established in 1994, becoming the 505th refuge in the National Wildlife Refuge System (NWRS). The Refuge boundary encompasses about 17,640 acres; this includes a core Refuge area of about 9,000 acres and a 9,000 acre "Cooperative Wildlife Management Area" where the Service first seeks to enter into cooperative agreements and memoranda of understanding with landowners or purchase conservation easements.. The Service actively manages about 6,200 acres. The Refuge is located in the Beach-Stone Lakes Basin within the Sacramento Valley in southwestern Sacramento County; it lies about ten miles south of the city of Sacramento, straddling Interstate-5 from the town of Freeport south to Lost Slough.