- Lake Pend Oreille (/ˌpɒndəˈreɪ/ POND-ə-RAY) in the northern Idaho Panhandle is the largest lake in the U.S. state of Idaho and the 38th-largest lake by area in the United States, with a surface area of 148 square miles (380 km2). It is 69 kilometres (43 mi) long, and 1,152 feet (351 m) deep in some regions, making it the fifth-deepest in the nation and having a volume of 43,939,940 acre feet = 54 km3. The lake is fed by the Clark Fork River and the Pack River, and drains into the Pend Oreille River, as well as subsurfacely into the Spokane Valley–Rathdrum Prairie Aquifer. It is surrounded by national forests and a few small towns, with the largest population on the lake at Sandpoint. The majority of the shoreline is non-populated and all but the southern tip of the lake is in Bonner County. The southern tip is in Kootenai County and is home to Farragut State Park, formerly the Farragut Naval Training Station during World War II, of which a small part is still active and conducts U.S. Navy acoustic underwater submarine research.