According to the United States Census Bureau, the city has a total area of 22.6square miles (59Square kilometers), of which, 22.3square miles (58Square kilometers) of it is land and 0.4square miles (1.0Square kilometer) of it (1.63%) is water. Rockwall is a city in Rockwall County, Texas, United States, and a suburb of Dallas. It is part of the Dallas/Fort Worth Metroplex. The population was 37,490 at the 2010 census. It is the county seat of Rockwall County. Rockwall County is the second wealthiest county in the state of Texas in terms of median income. The majority of its residents enjoy a relatively high standard of living. The name Rockwall is derived from a naturally jointed geological formation, which has the appearance of an artificial wall.