This visualization shows how formal US territorial control expanded in North America from 1700 to 1900, as seen through changes in the spatial distribution of post offices:
(HD and 1080p download here. It’s much prettier!)
A few months ago, I scraped post office location information from the USPS Postmaster Finder, and then extracted lat/long coordinates by correlating placenames to the USGS GNIS. Recently I remembered I had this data sitting around. I’ve been experimenting with Processing a lot lately as a tool for geographic visualization, and decided this would be an interesting dataset to use as a first stab at animation/dynamic mapping. I used parts of zipdecode from Ben Fry’s excellent book Visualizing Data as a foundation for my code. After some frustrations, this visualization is the result.
Of course, there are a few caveats: the USPS admits that their post office data is a constant work in progress, so there are likely many offices that aren’t shown on this map. About 10% of the placenames in the USPS data failed to find any coordinate matches in the GNIS data, so those don’t show up either. Finally, the USPS data includes closing dates for many offices, but these aren’t represented on the map, which might give a false sense of density in some areas.
Still, I think the results are pretty interesting. I’m no historian, but here are a few interesting patterns I’ve noticed aside from general westward expansion:
- 1776 – Several new post offices crop up along the east coast after the Revolution.
- 1846 – Rash of openings in Texas after statehood and the end of the Mexican-American War.
- 1848 – First offices established on the west coast, with lots of activity afterwards, likely due to gold rushes and CA statehood.
- 1851 – New Mexico and Utah start to see some activity as they become territories. I especially like the lines extending from Santa Fe along the Rio Grande / El Camino Real.
- 1860s – No activity in the South during the Civil War; also an interesting sweep across the Great Plains, with Oklahoma remaining conspicuously quiet.
- 1870s – Distinct traces along railroads in Nebraska and Kansas.
- 1890s – Oklahoma lights up due to several land rushes.
Anyone notice anything else interesting? Let me know.
Update: Very cool parallels to this visualization of newspapers in the U.S. 1690 to 2011, from Stanford’s Rural West Initiative!