was named for Chief Tenaya, leader of the Ahwahnechee. Of the many Native American peoples who lived on the Merced River, the most prominent were the
Miwok (consisting of
Plains Miwok and
Sierra Miwok),
Paiute, and
Ahwahnechee. Plains Miwok settled in the lowlands along the lower Merced River. The Sierra (or Mountain) Miwok lived in the upper Merced Canyon and in Yosemite Valley; at the time of first European contact, there were about 450 Sierra Miwok split among ten permanent villages. Paiute people, originally from the eastern Sierra near
Mono Lake, also lived in the upper watershed. The
Sierra Miwok and
Mono Lake Paiute, through cultural interaction over time, formed a distinct group, the
Ahwahnechee, whose name derives from
Ahwahnee, meaning "the valley shaped like a big mouth"a reference to the U-shaped Yosemite Valley. In the early 19th century, several military expeditions sent by
Spanish colonists from coastal California traveled into the Central Valley. One, headed by lieutenant
Gabriel Moraga, arrived on the south bank of the Merced River on September 29, 1806. They named the river
Río de Nuestra Señora de la Merced (River of Our Lady of Mercy); the
Virgin of Mercy is the patron saint of the diocese of Barcelona, celebrated on September 24. Another expedition in 1805 similarly named the
Kings River upon reaching it on January 6, the feast of the
Epiphany. Moraga's expedition was part of a series of exploratory ventures, funded by the Spanish government, to find suitable sites for
missions in the Central Valley and the Sierra Nevada foothills. In 1808 and 1810, Moraga led further expeditions along the lower Merced River below Merced Canyon, each time without result. Plans to establish a mission chain in the valley were eventually abandoned. In 1855,
Merced County was created, named after the river. Following the establishment of Merced County and California's independence from Mexico, settlers came to the Merced River area and founded small towns. One of the first was
Dover, established in 1844 at the confluence of the Merced with the San Joaquin. Dover functioned as an inland port where boats delivered supplies from the
San Francisco Bay area to settlers in the San Joaquin Valley. Other towns followed, including
Hopeton,
Snelling, and
Merced Falls, the last named for a set of rapids on the Merced near the present-day site of McSwain Dam. In the late 1880s, a
flour mill,
woolen mill, and several
lumber mills were built at Merced Falls. The Sugar Pine Lumber Company and Yosemite Lumber Company operated mills there for over thirty years, relying on
narrow-gauge railroads to ship lumber from the Sierra Nevada along the Merced River. Following construction of the
Central Pacific Railroad and
Southern Pacific Railroad, many of the river towns were deserted. Several cities that did achieve prominence include
Merced and
Turlock, both located on the railroad. The
California Gold Rush in the 1850s brought increasing mining activity to Merced Canyon and Yosemite Valley. Many Native Americans in the area revolted, leading to armed conflict between miners and the Ahwahnechee. In 1851, the
Mariposa Battalion was formed to drive the remaining Ahwahnechee out of the valley into reservations. The Battalion fought an Ahwahnechee group led by
Chief Tenaya over the South Fork of the Merced River. They succeeded in removing most of the Ahwahnechee from Yosemite Valley, first to a reservation near
Fresno. Following the Gold Rush, the Ahwahnechee were allowed to return, but further incidents prompted a second battalion to drive them out again, this time to the
Mono Lake area. Many place names in the valley originated from the Mariposa Battalion's expeditions. Even before the establishment of
Yosemite National Park, tourists began traveling into Merced Canyon and Yosemite Valley as early as 1855. The first roads into Yosemite Valley were built in the 1870s. The first was the
Coulterville Road, originating at
Coulterville, followed by the
Big Oak Flat Road, a trading route from
Stockton to Merced Canyon. Environmental advocacy led by
John Muir and
Robert Underwood Johnson convinced the U.S. Congress to establish Yosemite National Park in 1890. The creation of the national park increased tourism to the valley and the Merced River, leading to construction of additional roads throughout the upper Merced watershed. Other national forests protecting more of the upper basin followed, including
Sierra National Forest and
Stanislaus National Forest. crossing Barrett Bridge in April 1926 The
Yosemite Valley Railroad, originally built to serve mineral deposits in Yosemite Valley and Merced Canyon, continued operating through the early 20th century carrying tourists to Yosemite along the Merced River.
El Portal Road, constructed through Merced Canyon in 1926, ended passenger service on the railway, but freight operations continued until the mid-1940s, when major flooding destroyed sections of the line. In the early 20th century, while the upper Merced basin lay mostly protected, the lower river became the focus of dam-building and irrigation diversions by the Merced
Irrigation District. The District built the
Exchequer Dam, completed in the mid-1920s and raised in the 1960s, as a water storage facility on the Merced River. Irrigation using water from the Merced River grew substantially until most of the
arable land around the riversome was under cultivation. By the late 1950s and early 1960s, irrigation in the San Joaquin Valley was so extensive that many rivers ran dry in sections. Upstream of the Merced's confluence with the San Joaquin, the latter river was usually dry, regaining flow only where the Merced entered. In the mid-20th century, diminished flow in the Merced River meant very few
salmon returned to spawn in the lower section. In 1991, the Merced River Hatchery was built beside the river just downstream of the Crocker-Huffman Diversion Dam, the lowermost dam on the Merced. Fall
chinook salmon travel up a
fish ladder into the hatchery's pools, which are supplied with water diverted from the river. Yosemite Valley sustained significant damage when the
river flooded between December 31, 1996, to January 5, 1997. The flood was the worst in park history. The Merced River at
Happy Isles peaked at 10,100 cubic feet per second during the flood. Total park damages were estimated at $178 million. In 2024,
The New York Times reported that farmers had drained significant volumes of water during the 2022 drought, leaving part of the Merced dry without authorities being aware. == River modifications ==