Ten Mile River drains a watershed of about 76,800 acres (31,080 ha) and flows generally southwest for 7 miles (11 km) to the Pacific Ocean at the northern border of MacKerricher State Park, about 9 miles (15 km) north-northeast of the Noyo River at Fort Bragg and 5.7 miles (9.2 km) south of Westport, California. The mainstem begins at the confluence of the North Fork Ten Mile River and the Middle Fork Ten Mile River which are each about 15 miles (24 km) long and begin at an elevation of about 2,400 feet (732 m). The name Ten Mile refers to the distance north from the Noyo River. The Ten Mile watershed is in the California Coast Range which in this area is underlain almost entirely by the Coastal Franciscan Complex composed of a relatively homogeneous sequence of interbedded sandstone and argillite with some pebble and cobble conglomerate, and scarce amounts of limestone, chert, and basalt. The sedimentary rocks, for the most part, represent turbidites and other massive type deposits interpreted as ocean trench and trench-slope deposits that accumulated in an east-dipping subduction zone along the western margin of North America during Late Cretaceous and Early Tertiary time. Along the California coast, up to four major phases of dune formation have occurred since the middle of the Pleistocene, or roughly one million years ago, and continued to about 7,000 to 4,500 years ago. These ancient dunes have been buried by the build-up of more recent dune formations. MacKerricher State Park includes approximately 1,300 acres (530 ha) of dunes that developed episodically about 1500 years ago, 900 years ago, and 550 to 500 years ago. Coastal dunes generally form downwind of major river mouths such as the Ten Mile River that supply the sediments. The river’s connectivity to the ocean depends on flow discharge, which is a function of precipitation. Under low flow conditions during prolonged droughts, sand bars build at the river mouth constricting and often blocking it entirely. When this occurs, the estuarine portion of the Ten Mile River temporarily becomes a freshwater lagoon. Estuarine conditions return when large storm events cause a breach in the sand barrier and ocean connectivity is re-established. Despite the episodic connectivity, the river and estuary provide important fish habitats for anadromous and marine fishes but this varies seasonally and annually.

Tribes of the Pomo and Yuki peoples lived in or traveled through the region of the Ten Mile River utilizing resources such as deer, fish, seaweed, shellfish, and acorns. The Pomo are descendants of Hokan-speaking people that are widely distributed along the California coast and centered at the Russian River. The Chedilna tribe of the Pomo had a village at the mouth of the Noyo River called Kadiu. Houses were made from slabs of bark leaned together into a cone 10 to 15 feet (3-4.5 m) in diameter. In 1855, an exploration party from the Bureau of Indian Affairs visited the area looking for a site on which to establish a reservation, and in the spring of 1856, the Mendocino Indian Reservation was established along the coast roughly from Ten Mile River in the north to the Noyo River in the south. The Pomo were the first to be forcibly moved to the reservation followed by neighboring peoples of the Yuki, Wappo, and Whilkut. In 1857, a military post called Fort Bragg was established on the Mendocino Indian Reservation to maintain order and subjugate the Native Americans. In 1862, U.S Army troops were withdrawn from Fort Bragg to fight in the American Civil War, and they were replaced by a detachment of the California Infantry. Also in 1862, a mill worker named Duncan MacKerricher got a job assisting Indian Agent E.J. Whipple on the Mendocino Indian Reservation. Later that same year, the Fort Bragg garrison was loaded aboard the steamer Panama of the Pacific Mail Steamship Company and abandoned the military post. In 1864, the Native Americans who lived there were forcibly removed to the Round Valley Reservation, which was at that time called the Nome Cult Farm. The Mendocino Indian Reservation was discontinued in 1866 and the land opened for settlement three years later. Duncan MacKerricher and his wife Jessie bought an area of the former Mendocino Indian Reservation known as El Rancho de la Laguna. There they established a successful working ranch that produced butter, grew potatoes, and was known for its draught horses. MacKerricher is also said to have employed many Native Americans on his ranch, as many as half the Pomo who had been living on that reservation. In 1949, their descendants sold the property to the state of California which became a state park that opened in 1952.

The Ten Mile River basin has been logged continuously since the early 1870s when trees were cut using single-bladed axes and dragged by oxen to mills at Fort Bragg. In 1883, a wharf was built at Laguna Point about 5 miles (8 km) south of the river mouth to load redwood lumber schooners bound for San Francisco. Ox teams were replaced by railroad lines in the early 1900s, and in the 1930s, the railroads were replaced by tractor roads. In 1973, the California Forest Practice Act banned destructive tractor logging on steeper slopes. The timber on both sides of the river was logged by the Georgia Pacific Company until 1999 when the company was acquired by the Hawthorne Timber Company. Historically, the Ten Mile River had an important coho salmon population, but the spawning population has decreased from an estimate of 6,000 fish in the early 1960s to between 14 and 250 in the 1990s. Contributing factors to this decline include natural variability exacerbated by excessive sedimentation from logging, increased water temperatures due to the removal of riparian vegetation, and reduced woody debris in salmon habitats. Improved timber harvest practices and regular road maintenance have reduced sedimentation in about 45 percent of the watershed. In 2012, the California Fish and Game Commission designated the Ten Mile area as a marine protected area marking the completion of the first statewide network of underwater parks in the United States. The marine reserve network now protects California coastal areas and important wildlife and habitats which help the state’s tourism industry, hotels, and restaurants that depend on healthy fish populations. The Ten Mile River Estuary, Ten Mile Beach, and Ten Mile State Marine Reserve form a marine protected area of 10,050 acres (4,070 ha) that extends from the estuary out to sea for 5 nautical miles (9 km). Read more here and here. Explore more of the Ten Mile River and MacKerricher State Park here: