Copeville is an unincorporated community in southeastern Collin County, Texas, United States, along State Highway 78. Its elevation is 554 feet (169 m). Although Copeville is unincorporated, it has a post office, with the ZIP code of 75121; the post office was first opened in 1878. Named for early settler Miles Cope, the community was founded in the 1850s. It moved about a mile from its original location to its current site after the [name] was built through the area: residents wanted to have railroad access. Copeville has declined in the last century, becoming only a shadow of its pre-Depression size.