Pioneer (formerly, Pioneer Station) is an unincorporated community in Amador County, California. It is located 5 miles (8.0 km) east-northeast of Pine Grove, at an elevation of 2986 feet, along State Route 88. The community is in ZIP code 95666 and area code 209. Pioneer was a stage stop for the Pony Express riders, and the old Pioneer Station still stands. A post office opened in Pioneer in 1957.