Although the settlers had hoped to have their county named Castle County, by act of the legislative assembly in 1880 it was given the name of Emery County in honor of Territorial Governor George W. Emery. Castle Dale was made the county seat.

In the spring of 1878 Sylvester Wilson and his brothers, with their families, and Charles Swasey and brothers, located on a spot five miles east of Castle Dale which was given the name of Wilsonville. During the year an overland mail route was established between Salina and Ouray, Colorado, a post office being set up here with Sylvester as postmaster —the first in Castle Valley. He was also granted the contract to carry the mail over this route, called the Star Mail Route.

The mail was brought by horseback from Sanpete County via Salina Canyon, the first settlers receiving it only once a month. One year John K. Reid spent the winter in Manti. In the spring he brought with him two sacks of letters which had accumulated in Salina.

In 1878 the initial settlement on Cottonwood Creek petitioned for a post office for "Castle Vale." The following year, John Reid received a commission as postmaster, but the name had been changed to Castle Dale. The office was set up in the Reid dugout in Orangeville, which at that time was known as Upper Castle Dale, but he had to go to Wilsonville for quite some time to open the mail pack. In November Castle Dale was given a separate pouch and men took turns going to Wilsonville to carry the mail.