Eastdale, ColoradoEastdale is an extinct town in Costilla County, in the U.S. state of Colorado. Eastdale was a farming community on the Colorado/New Mexico border.HistoryEastdale was laid out in 1890. The Eastdale post office operated from April 27, 1895, until July 15, 1909. The San Luis, Colorado, post office serves the area. A large share of the first settlers were Mormons.