Hi All--I am working on a project that involves mapping changes to roads over the 50 year period starting in 1964 (the result will be released in 2014). Anyone out there aware of historic digital data showing the road network in the USA? I'm also seeking data for public land ownership/management from the same time period. I've already found great Census boundaries and tabular data from the 1960 decennial Census at https://www.nhgis.org/, and it looks like USGS has scanned and made freely available all of their old topo maps at http://nationalmap.gov/historical/, but I am trying to avoid having to digitize the entire USA! There is interest from the historic project at OSM if we need to go that route, but even with crowd-sourcing, it would be a tremendous effort. Any help is much appreciated!