Clayton prospered during the coal mining boom in eastern Contra Costa County. The post office opened in 1861. Following a previous incorporation attempt in 1960, Clayton incorporated in 1964 in order to stave off an annexation attempt in 1963 of the Cardinet Glen neighborhood by nearby Concord. After steady expansion during the 1970s to the east and west from its original boundaries, Clayton's land area more than doubled in 1987 to near its present-day boundaries with the annexations of the Dana Hills/Dana Ridge and Clayton Wood subdivisions, as well as the former Keller Ranch property that was developed during the 1990s with the Oakhurst Country Club.
Clayton prospered during the coal mining boom in eastern Contra Costa County. The post office opened in 1861. Following a previous incorporation attempt in 1960, Clayton incorporated in 1964 in order to stave off an annexation attempt in 1963 of the Cardinet Glen neighborhood by nearby Concord. After steady expansion during the 1970s to the east and west from its original boundaries Clayton's land area more than doubled in 1987 to near its present-day boundaries with the annexations of the Dana Hills/Dana Ridge and Clayton Wood subdivis,ions, as well as the former Keller Ranch property that was developed during the 1990s with the Oakhurst Country Club.