Alta is a small unincorporated community and census-designated place in Placer County, California, United States, about 30 miles northeast of Auburn. The village is located off Interstate 80 and along the historical First Transcontinental Railroad. The ZIP code is 95701 and the area code 530. One of the few buildings other than private residences is the Alta-Dutch Flat Grammar School serving kindergarten through eighth grade students. The high school that serves Alta is Colfax high School. Colfax High School is 11 miles southwest in the incorporated town of Colfax. The population of Alta was 610 at the 2010 census.A historical California place once named Alta was located in San Diego County near the present-day La Mesa–El Cajon boundary. This historical place was along the San Diego and Arizona Eastern Railway, now the San Diego Trolley Orange Line, at its Murray Drive undercrossing in La Mesa. The community was named after the Spanish word meaning "upper" or "high".