Addison is an incorporated town in Dallas County, Texas, in the United States. Addison is situated to the immediate north of the city of Dallas. The town's population was 13,056 at the 2010 census. Addison and Flower Mound were the only two Texas towns with a population greater than 10,000 in the 2010 census; since then the towns of Prosper and Trophy Club have also exceeded 10,000 in population estimates.