tarrant_county,_texas | countyseat | fort_worth,_texas <tsp> arlington,_texas | ispartof | tarrant_county,_texas <tsp> arlington,_texas | ispartof | texas <tsp> 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. texas. u.s. fort worth is the county seat of tarrant county. the biggest city in texas is houston.it is texas' third-most populous county and the 15th-most populous in the united states