Fascinating. They moved the entire wall?! Do you know approximately when this was done and why?
The original east wall was removed in 1901 to make room for the present Lady Chapel and two apsidal chapels pictured here:
At that moment, a new parish was organized in the Hamilton Heights neighborhood and its first pastor was a long-time priest at St. Patrick's. He used the east wall of the cathedral and the facade of the National Academy of Design, pictured here:
which was being taken down as well, and cobbled together a church for less than building new.
Quite a resourceful guy.