JOHNSVILLE, TEXAS. Johnsville, just off U.S. Highway 67 and fifteen miles southeast of Stephenville in southeastern Erath County, was named for its first postmaster, John Martin. The community had a post office, a store, and fifty residents in 1940. By 1980 its population had declined to twenty-five, and its post office had been closed. Through 2000 the community's population was still reported as twenty-five.