 However, it seems more plausible that the county was named for the town of San Augustine, which had been established five years earlier and whose name was based upon an 18th-century Spanish presidio (fortress), the Presidio de San Agustín de Ahumada, named for Agustín de Ahumada, 2nd Marquess of Amarillas.According to the U.S. Census Bureau, the county has a total area of , of which is land and (10%) is water.As of the census of 2000, there were 8,946 people, 3,575 households, and 2,520 families residing in the county.