Thanks for all your comments. I figured I could rely on Freepers to fill me in.
The Tappan Zee Bridge was built across the widest part of the Hudson River (the word "zee" is Dutch for "sea"). It was built in its current location in order to ensure that it would lie just north of the northern jurisdictional boundary of the Port Authority of New York & New Jersey -- thereby allowing New York State to build and operate the bridge on its own without having the toll revenue go to the bi-state agency.