Pacheco is a census-designated place (CDP) in Contra Costa County, California, United States, in the San Francisco Bay Area. The population was 3,685 at the 2010 census. It is located 5.5 miles (9 kilometres) north of Walnut Creek, 19 miles (31 km) miles northeast of Oakland, California, and 27 miles (43 km) miles northeast of San Francisco.
According to the United States Census Bureau, the CDP has a total area of 0.7 square miles (1.8 square kilometres), all of it land.
This region experiences warm (but not hot) and dry summers, with no average monthly temperatures above 71.6 °F. According to the Köppen Climate Classification system, Pacheco has a warm-summer Mediterranean climate, abbreviated "Csb" on climate maps.
The town was laid out in 1857 by Dr. J. H. Carothers and named for Salvio Pacheco, grantee of the Rancho Monte del Diablo Mexican land grant. A post office operated at Pacheco from 1859 to 1913 and from 1955 to the present.
Pacheco was briefly a prosperous commercial center. During this period, Pacheco Slough was deep enough to receive ocean-based shipping. From 1851 to nearly 1873, Pacheco was the county’s commercial center: the shipping port for the grain grown in the Ygnacio, San Ramon and Tassajara valleys, with warehouses, a flour mill and shops along the creek. Walnut Creek, (then known as Pacheco Creek), then flowed deep and free into Suisun Bay. For over 20 years, Pacheco was a major shipping port for central Contra Costa County.
The destruction of Pacheco’s Walnut Creek shipping channel occurred gradually over many years and for many reasons.