Decatur is a city located in Wise County, Texas, United States. This city was named after Stephen Decatur, Jr. As of the 2007 census, the city had a total population of 15,478. It is the county seat of Wise County. Decatur is part of the Dallas/Fort Worth Metroplex and is located 25 miles northwest of Fort Worth and 45 miles northwest of Dallas. Decatur is one of the fastest growing cities in Texas, while Wise County is the fourth fastest growing county in Texas.