Complex sentence: Bergen County's population resides among 70 municipalities--but no large cities--as its most populous place, with 43,010 residents at the time of the 2010 Census, is Hackensack, also its county seat.
Split into simpler sentences: Bergen County's population resides among 70 municipalities but no large cities. Its most populous place, with 43,010 residents at the time of the 2010 census, is Hackensack, also its county seat.