Rodeo is a census-designated place (CDP) located in Contra Costa County, California on the shore of San Pablo Bay. The population was 8,679 at the 2010 census. The town is named for the livestock roundups common in the late 19th century. Cattle from the surrounding hills were regularly driven down through the old town to a loading dock on the shoreline of San Pablo Bay for shipment to slaughterhouses, a practice which continued through the early decades of the 20th century. The town of Rodeo is served by the Interstate 80 freeway and State Route 4. The Southern Pacific Railroad main line passes through Rodeo; however, Rodeo has not been a stop on the railroad since the 1950s.