tarrant_county,_texas | countyseat | fort_worth,_texas <tsp> arlington,_texas | ispartof | tarrant_county,_texas <tsp> arlington,_texas | ispartof | texas <tsp> tarrant_county,_texas | country | united_states <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 is part of tarrant county in the state of texas but houston is the largest city there. tarrant county. texas is located within the united states and their county seat is fort worth.it is texas' third-most populous county and the 15th-most populous in the united states