This site catalogs historical USGS topo maps and makes them available as layers that you can easily toggle on and off. There is a transparency slider so you can easily compare historical maps with each other or with the current basemap. The map layers can also be downloaded.
TopoView provides a nice map interface to USGS’s Historical Topographic Map collection. Download GeoTIFFs, JPGs and KMLs at various scales for different uses.
EarthExplorer offers aerial imagery that’s unavailable elsewhere—some of it dating back to the 1950s. Fill in your search criteria and then, on the data sets tab, select “aerial photo single frames” or “high resolution orthoimagery”. The Results tab will show the available images for your search.
PASDA offers some tiles I haven’t found elsewhere, like LIDAR of the whole state, and black and white aerial imagery (à la TerraServer) from the 90s. These are great for locating old roads, trails and waterways. Note: as of July 2020, this website replaces Penn Pilot. It contains all the same imagery and more.
This page is somewhat confusing, but it offers good background information on the project. I prefer to use this search: US Topo and Historical Topographic Map Collection to go directly to historical topos, if I know the quad name.
Hate the new Google Maps? You’re not alone. Barry Hunter has created KMLMaps (formerly ClassyGMaps), which uses the Google Maps API to restore much of the old (and extremely useful!) functionality of previous iterations of Google Maps. Use the link above in your browser or grab the source code from GitHub.
These maps aren’t strictly related to survey mark hunting, and most don’t indicate any benchmark locations, but they’re an excellent resource for anyone hiking or hunting in our national parks.
Numidia Airport is the home of a lovingly restored tower beacon and caretaker’s shanty. The airport’s owner has provided a detailed history of the airport and the U. S. Airmail system.
Hiding in plain sight, massive arrows—about fifty to seventy feet long and made of concrete—lie across the country, slowly succumbing to the ravages of time. First published in Oklahoma Today Magazine.
They’re oftentimes visible only from the sky. They point in seemingly random directions. They’re about 70 feet long and made of deeply sun-bleached concrete. What are they? First published in Blue Ridge Country Magazine.
Learn about the characteristics, operation and maintenance of airway beacon facilities, from the early acetylene-powered beacons to the familiar Crouse-Hinds DCB-36 beacons!