The University of New Hampshire Library has put online a digital collection of old topo maps of New England and New York. Very high-resolution scans.

This online collection of over 1500 USGS topographic maps includes complete geographical coverage of New England and New York from the 1890s to 1950s.

I have the strange feeling that I’ve either seen or posted this before, but it doesn’t seem to be in the archives. Via Plep.