Complex sentence: The Newkirk Viaduct Monument was erected in 1838 at the completion of the Gray's Ferry Bridge in Philadelphia, then known as the "Newkirk Viaduct" a monumental obelisk was erected to commemorate is completion.
Split into simpler sentences: The Newkirk Viaduct Monument was erected in 1838 at the completion of the Gray's Ferry Bridge in Philadelphia. Then known as the "Newkirk Viaduct" a monumental obelisk was erected to commemorate is completion.