tarrant_county,_texas | countyseat | fort_worth,_texas <tsp> texas | capital | austin,_texas <tsp> arlington,_texas | ispartof | tarrant_county,_texas <tsp> arlington,_texas | ispartof | texas <tsp> texas | largestcity | houston <sep> tarrant county is located in the us state of texas as of 2020, it had a population of 2,110,640 it is texas' third-most populous county and the 15th-most populous in the united states its county seat is fort worth 
arlington (the capital of texas) is located in tarrant county. fort worth is the county seat of tarrant county.tarrant county texas texas is the third-most populous county in the united states