Decatur is located in Wise County, (of which it is the county seat), 40 miles northwest of Fort Worth, where US 287 and US 380 meet, on the Burlington Northern Railway.
Growth since the 1960s is attributable in part to the influx of people who commute to Fort Worth. In 1988 Decatur had 4,523 residents; it was a center for petroleum production, clothing and glass manufacture, and marketing and processing for Wise County agribusiness.
The population in 1990 dropped a little, to 4,252.