Greenhorn is a non-populated city in Baker and Grant counties in the U.S. state of Oregon. It straddles the Blue Mountain ridge, so that it is located in both Grant County and Baker County. As most of the city is situated in Baker County, and the early residents considered Baker City to be more convenient, for administrative purposes it is considered to be in Baker County.As of the 2000 census, the city had a total population of 0.