Little Rock Creek's originates just west of the summit of Mount Williamson and flows down the north slope of the San Gabriel Mountains. Its main tributaries are South Fork Little Rock Creek and then Santiago Canyon Creek just before reaching Little Rock Reservoir. At Little Rock Dam it becomes Little Rock Wash which terminates in the Antelope Valley. Little Rock Creek is part of the Antelope Valley Watershed, which is a closed endorheic basin with no outlet. It is part of the South Lahontan Hydrologic Region.