The Dr. William M. Scholl Center for American History and Culture has released a set of shapefiles for historical state and county boundaries from 1629 to 2000 as part of their Atlas of Historical County Boundaries. These shapefiles are very useful for creating historical maps, so I’ve bundled them with a few convenience functions as the USAboundaries package for R. This package makes it easy to make a map for any arbitrary day in United States history.
library(USAboundaries) library(sp) map_1844 <- us_boundaries(as.Date("1844-03-21")) plot(map_1844)
For more, see the documentation. The package is available on CRAN.