Midpines is a census-designated place in Mariposa County, California. It is located 12 miles southwest of El Portal, at an elevation of 2585 feet. It lies among the Sierra Nevada foothills of the central part of the state, 6 to 10 miles north of Mariposa, the county seat. It is composed of scattered residential areas along both sides of State Route 140, which is one of three principal routes to Yosemite National Park, some 30 miles to the east of Midpines. The population was 1,204 at the 2010 census.Midpines began as a resort, founded by Newell D. Chamberlain, in 1926. The first post office opened in 1929.