Lancha Plana ("flat boat" in Spanish; formerly, Sonora Bar) was a small settlement in Amador County, California, formed as a result of a flatboat ferry crossing across the Mokelumne River. It was founded by Mexican settlers in 1848. It lay on the north bank of the Mokelumne River, 9 miles (14 km) south-southeast of Ione, at an elevation of 220 feet (67 m). The remnants of the town were submerged as a result of the damming of the river to form the Camanche Reservoir.