From I-10E exit 8th St. in Banning, California, turn right onto 8th St, then left on Lincoln St. then right on San Gorgonio Ave/Highway 243. From I-10W exit Hargrove St, turn left onto Hargrove St,the right on Lincoln St. then left on San Gorgonio Ave/Highway 243. Go South on 243 for approximately 17.5 miles to Black Mountain Rd (4s01 dirt road) travel approximately 6milesto Boulder Basin Campground. Note: Black Mountain Road (4S01) is an unpaved forest road not recommended for low clearance vehicles or trailers.