Walnut is a city in the San Gabriel Valley of eastern Los Angeles County in the U.S. state of California. According to the 2020 census, the city had a population of 28,430.
The greater Walnut Valley is located between the steep San Jose Hills to the north and the gently sloping Puente Hills to the south. Quality housing consists of master-planned single family homes ranging in size from . The city hosts a highly ranked public school system: the Walnut Valley Unified School District, which has been ranked by numerous sources as one of the top public school districts in Southern California, as well as Mt. San Antonio College.
The city covers nearly and is home to hundreds of businesses. According to the 2023 census bureau estimate, Walnut has a median household income at one of the top-earning percentiles in the country at $133,762.
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History
thumb|left|[[Californio ranchero Ricardo Vejar owned both Rancho Los Nogales and part of Rancho San José, which make up modern-day Walnut.]]
The area are the traditional lands of the Tongva people. Spanish missionaries who arrived in the 18th century called the indigenes Gabrieleño, because the area where they lived was controlled by the San Gabriel Mission. The Walnut area was part of the network of outlying ranches used for the grazing of cattle and sheep by the Mission.
Following secularization of the missions in the 1830s, former mission lands were divided into ranchos, and given away as land grants by the Mexican government of Alta California. In the Walnut area, the first grants were Rancho San Jose (granted to Ricardo Vejar and Ygnacio Palomares in 1837); Rancho Los Nogales (granted to Jose De La Cruz Linares in 1840); and Rancho La Puente (granted to John Rowland and William Workman in 1842). In 1868, John Rowland and William Workman divided Rancho La Puente, leaving Rowland the eastern half and Workman the western half. Rowland's land included the western portion of Walnut and the adjacent community now called Rowland Heights. The land was used mainly for raising cattle and growing wheat, grapes, and fruit trees (mostly citrus).
In 1895, the first U.S. post office was established and given the name "Lemon". In 1908, the post office name was changed to Walnut. As a reminder of those early days, the U.S. Post Office is on Lemon Avenue, one of the town's main streets.