A professor at the University of Waterloo created an interactive map with 49,603 historic points of interest. It's meant to be a research project, but it's actually a pretty fun tool for browsing sites and planning travel.
Along with a team of researchers, professor William Cook spent two years solving the Travelling Salesman Problem with historic sites. The problem aims to find the most efficient route between multiple destinations, with the goal to end up in the original destination. Cook pulled 49,603 spots from the National Register of Historic Places, then used data from Google Maps to find the quickest possible route between them.
You're probably not going to take the 350,201km route that Cook and his researchers plotted out, but you can explore the interactive map, which includes almost 50,000 points of interest.
Read more about the project here, then head to the link below to explore the map.