Greenhorn City is a nearly unpopulated community located in Baker and Grant counties in Oregon. It straddles the Blue Mountain ridge, so that it is located in both Grant County and Baker County. As most of the town 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. It received its name from being located in the Greenhorn Mountains.

There was a significant rush to find gold in the mountains of northeast Oregon in the 1860s and several small mining communities were established in the region. One of the first settlements in the immediate area was Robinsonville but it burned down in 1898. Greenhorn City was first populated during this gold rush as miners prospected for gold in the area. The mining district was composed first of placer mines, but soon many lode gold mines developed. Greenhorn City experienced a boom shortly after the turn of the 20th century. A post office was established as Greenhorn on May 24,1902 with Burton Miller serving as the first postmaster. The town was platted in 1903 and was soon incorporated. At 6,296 feet above sea level, Greenhorn City was the highest incorporated community in Oregon. It is unique in that it was established on land that was originally patented from the United States for the purpose of platting the city (rather than being homesteaded by individuals).

During its boom days, 1910-1915, the city of Greenhorn housed two hotels, a post office, waterworks including fire hydrants, a number of general merchandise and grocery stores, several saloons, one house of prostitution, and later a wooden jail. The population was listed as 28 in the 1910 census. The post office was closed on December 15, 1919.

In later years, the old Greenhorn jail was removed to Canyon City under suspicious circumstances. A court case ensued for its return, but because the city straddles the Blue Mountain ridge, the district attorneys of Baker County and Grant County could not even agree in which courthouse it should be held. The case was eventually heard by the Circuit Court for Grant County in Canyon City, Oregon. The jail remains in Canyon City, Oregon. The community continued until 1942 when gold mining was made illegal by Federal Public Law 208 during World War II. It is essentially a ghost town today with only an intermittent population ranging between zero and three with a scattering of buildings.

Contributed by Steve Lent, historian