Ephrata was incorporated on June 21, 1909 and the county seat for the newly created Grant County and generally believed that the city was named Ephrata by a man who worked for the Great Northern Railroad.

At the turn of the century great herds of wild horses that roamed the land, as Horse trading was an important element of the local economy, served as the staging area for the horse round-ups. The last "Grand Horse Round-up" was held in Ephrata in 1906, then developed as a trade and service center for cattle and sheep ranches in the area until the construction of the Columbia Basin Reclamation Project.