Byron is a census designated place (CDP)[6] in Contra Costa County, California, United States.

Byron's location was part of a land grant that Jose Noriega received from the King of Spain in 1835.

In 1841, the Bidwell-Bartelson wagon train arrived at Marsh's ranch with the earliest Anglo settlers from the east.

[8] Byron is named after an employee of the San Pablo, and the eastern U. S. and Pacific Railroad.

[a] In 1942, all of the town's residents of Japanese descent were forcibly removed by the US government with pressure from California agricultural interests and taken to Turlock assembly center.

[9][10] In 1960, Contra Costa County built the Orin Allen Youth Rehabilitation Center, better known informally as the Boys' Ranch on a 50 acres (200,000 m2) tract immediately southeast of Byron.

The property has no security fence to contain residents within the perimeter and includes dormitories, classrooms, a kitchen and dining facility, athletic facilities and administrative offices which occupy about one-third of the area.

[11] In 2008, a Contra Costa County Grand Jury began an investigation into whether the facility was cost-effective, or whether it should be permanently closed.

[11] According to the United States Census Bureau, the CDP has a total area of 6.5 square miles (17 km2), all of it land.

There were 415 housing units at an average density of 64.0 per square mile (24.7/km2),of which 389 were occupied, 254 (65.3%) by the owners and 135 (34.7%) by renters.

[33] In 1938 the resort closed, after a series of lawsuits that were probably brought about by the Great Depression, but was leased by the government in 1941 and became a military interrogation camp housing both German and Japanese prisoners of war, known as Camp Tracy, until 1945, when orders were sent to dismantle it.

[34] In 1947 Byron Hot Springs was put up for sale and purchased by the Greek Orthodox Church for $105,000.

It then changed hands several times as a resort, country club, and private residence.

[8] In 1993 Contra Costa County broke ground on a new airport two miles (3 km) south of Byron.

814 acres (3.29 km2) are reserved for habitat management land for the San Joaquin kit fox, a federally listed endangered species, as well as many other endangered and special status species.