The entrance to Mammoth Bar is located on Old Foresthill Road. The easiest access is off of Interstate 80 north of Auburn. Take the Foresthill exit off I-80 and go east about 2.5 miles to the Old Foresthill Road. Turn right on Old Foresthill and the entrance is about 1.5 miles on the left.
Mammoth Bar trail maps are available at the park office and kiosk.