Byron is a census designated place 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. Noriega then sold 17,000 acres to John Marsh for the equivalent of $500. In 1841, the Bidwell-Bartelson wagon train arrived at Marsh's ranch with the earliest Anglo settlers fr…Byron is a census designated place 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. Noriega then sold 17,000 acres to John Marsh for the equivalent of $500. In 1841, the Bidwell-Bartelson wagon train arrived at Marsh's ranch with the earliest Anglo settlers from the east.