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 is in tarrant county which is part of the state of texas. the largest city of the county and state is forth worth.it is texas' third-most populous county and the 15th-most populous in the united states