- The Newberry Library has historical data on US county boundaries
- A Vision of Britain has historical data on UK counties and parishes
A solution to this problem is tracing historical maps. NYPL has a nice project called Map Warper which allows you to georectify digital scans of old maps. However, that's just one step of the process. After properly aligning the map, we want to trace and extract the historical boundaries.
So we're going to create our own map warper. Though it will be heavily inspired by the NYPL Map Warper, we're going to start from scratch. It will be written in node.js and include the second step of tracing the map after it's been georectified.
Sadly, this requires a small refactor of OPDs infrastructure, but we've already finished the first step.