We believe these maps have no known US copyright restrictions.* To the extent that some jurisdictions grant NYPL an additional copyright in the digital reproductions of these maps, NYPL is distributing these images under a Creative Commons CC0 1.0 Universal Public Domain Dedication. The maps can be viewed through the New York Public Library’s Digital Collections page, and downloaded (!), through the Map Warper. First, create an account, then click a map title and go. Here’s a primer and more extended blog post on the warper.Read the full announcement on their blog.
Visit the NYPL Digital Collections page.