OVERVIEW OF THE CITY OF DALLAS, TEXAS TX: Dallas is in Dallas county and is the county seat. Population is estimated at over 2 million. In 2018, the Dallas-Forth Worth area experienced the largest population growth of any other city in the United States. For more stats and info about Dallas, Texas, visit Dallas City Hall. The Trinity River runs through Dallas. To see plans for future development for the river area, visit The Trinity River Corridor Project.