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