Furnace is an Estill county community on KY 213 along the mountain south of Stanton and northeast of Irvine. It was founded about 1830 around the Estill Steam Furnace. The first post office in the area was known as Mountain Spring, which opened in 1854. It was soon after moved to the east and from 1857 until 1864 it operated as Estill Furnace. The Furnace post office opened in 1882 and closed in 1975. The population reached several hundred, but soon declined as the furnaces began closing in the 1870s. The ruins of several iron furnaces remain in the area.