The history of Brentwood dates back to a small blacksmith shop that was built in 1874. By 1878, Brentwood erected its first post office and the San Pablo-Tulare Railroad serviced the growing township. Its namesake is a city in England where a resident of the new town once lived.
By 1890, Brentwood became the largest shipping point for wheat and barley between New Orleans and San Francisco. It incorporated in 1948, the first in East Contra Costa County, but remains an agricultural town even today. Crops raised include grains, alfalfa, apricots, nectarines, peaches, plums, cherries, figs, pears, walnuts, almonds, pistachios, tomatoes, corn, melons, squash, and lettuce. In 1913, the Balfour Guthrie Investment Company installed a $500,000 irrigation system, allowing Brentwood to support thriving orchards of apricots, peaches and cherries. By the 1920s, Brentwood became well known as one of California's agricultural centers.
The first people to live in the area were the Native American tribe known as the Bay Miwoks or the Northern Valley Yokuts. They were peaceful people who enjoyed singing and dancing, and lived mostly on acorn gruel, fish, game, berries and seeds. They lived in dome shaped houses thatched with tulle.
Residents can see all that remains of this culture by visiting two abandoned village sites, known as Shell mounds. One is along Indian Slough and Marsh Creek roads and the other at the Caves of Vasco.
The first European explorer of Contra Costa County was Pedro Fages in 1772. But it wasn't until 65 years later that Europeans settled here. In the late 1830's, Dr. John Marsh became the first American citizen and physician in the area. He soon purchased a 12 X 10 mile grant for $500 and used the land primarily for cattle. In 1837, Dr. Marsh built a large stone manor house that still stands today, 2.5 miles south of Brentwood on Marsh Creek Road.