The Big River is a river in Mendocino County, California, that flows from the northern California Coast Range to the Pacific Ocean at Mendocino, Mendocino County, California. From the mouth, brackish waters extend 8 miles (13 km) upstream, forming the longest undeveloped estuary in the state. History Pre-European contact, the lands about the Big River belonged to the Me-tum’mah, or Mitom Pomo. This sub-tribe of the Northern Pomo lived in the area of Little Lake Valley near Willits and claimed the coast from south of the Noyo River at what is now Fort Bragg, to just north of the Navarro River, eighteen miles south. They had a settlement, Buldam, on the north bank of the river, near its mouth, but its exact location is unknown and stories about its date of settlement are conflicting. Big River was named for the giant redwoods that once lined its banks; it's shown as Arroyo Grande on a diseño of the Albion Mexican land grant of October 30, 1844. The timber industry has dominated the area since the 1850s, when the first mill was constructed in what was then known as Mendocino City (now Mendocino). The mill was constructed on the bluffs overlooking the river mouth with an apron chute to load finished wood onto ships was constructed at the mill. Splash dams were built on the river and their floodgates were opened every winter to sweep logs downstream to booms which kept the logs from floating out to sea. This method of log transport increased erosion, removed woody debris, and buried cobble substrates. Logging practices especially impacted the estuary, which served as a mill pond from 1852 to 1938. Watershed and Course The Big River watershed drains , from the northern California Coast Range to the Pacific Ocean at the town of Mendocino, about 10 miles south of Fort Bragg. The Big River watershed borders the watersheds of the Noyo River to the north, the Eel and Russian rivers to the east, and the Little, Albion, and Navarro rivers to the south. The river's headwaters start in the Mendocino Range, part of the California Coast Range at an elevation of approximately 2800 ft (865m), inland from the Pacific Ocean. The headwaters are partially fed by Montgomery Creek as it flows through the upland riparian habitat and virgin redwoods of Montgomery Woods State Reserve. From there, the river flows roughly west through Jackson Demonstration