tarrant_county,_texas | largestcity | fort_worth,_texas <tsp> arlington,_texas | ispartof | tarrant_county,_texas <tsp> arlington,_texas | ispartof | texas <tsp> tarrant_county,_texas | country | united_states <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 
in the united states. is tarrant county in texas. arlington is part of tarrant county and the largest city in the county is fort worth.it is texas' third-most populous county and the 15th-most populous in the united states