 In 1876, the state legislature defined and named the county, but it was not organized until 1890, with the town of La Plata as the original county seat.The county was named for Erastus "Deaf" Smith (1787–1837), a partially deaf scout and soldier who served in the Texas Revolution and was the first to reach the Alamo after its fall.The pronunciation of "Deaf", like that of Smith himself, is ; however, most residents pronounce it .