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. tarrant county (with its seat in fort worth). are part of texas. within the united states. texas has its largest city as houston.it is texas' third-most populous county and the 15th-most populous in the united states