Complex sentence: WUP moved to two former theological seminary buildings on North Avenue in Allegheny City (present-day North Side), remaining there for eight years, then moving to a site on the North Side Observatory Hill at the location of its Allegheny Observatory.
Split into simpler sentences: WUP moved to two former theological seminary buildings on North Avenue in Allegheny City (present-day North Side). The University stayed there for eight years before moving to a site on the North Side Observatory Hill at the location of its Allegheny Observatory.