Ye Olde New York Maps
Len, are you in or near NYC? The main branch of the New York Public Library, at Fifth Avenue and 42nd Street, has one of the world's top map collections including vintage maps of NYC.
But the NYPL collection might be overkill for your needs. If I may inquire, what exactly do you want to get from the maps you seek? Individual streets? Transportation lines? Town or ward boundaries? Or just geography?
(BTW, I do believe that the original 1811 Commissioners' Grid Plan is part of the N-Y Historical Society collection. If that's one of the things you're after, you'll find it reproduced in many, many reference sources.)