Marsh Creek Road is an approximately twenty-one-mile rural highway in the Diablo Range of Contra Costa County, California. The roadway begins in the city of Clayton near Mount Diablo and follows the namesake Marsh Creek to the outskirts of Discovery Bay. Since 2012 a portion of Marsh Creek Road between Vasco Road and Byron Road has been signed as part of California State Route 4. The highway is named after Alta California settler John Marsh who settled in the area during 1838.
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