Complex sentence: It was one of the five original squares laid out on the city grid by Penn and the geographic heart of the city from 1682 until the Act of Consolidation, 1854 (although it was never the social heart of the city during that long period).
Split into simpler sentences: It was one of the five original squares laid out on the city grid by Penn. It lay at the geographic heart of the city from 1682 until the Act of Consolidation, 1854 (although it was never the social heart of the city during that long period).