The data used in the Atlas project is readily available to download to be consulted, reviewed, and reused for any lawful purpose, commercial or non-commercial, without licensing or permission fees to the library. Please note that some of these files contain the original, out-of-date copyright license; these can be ignored. For ideas about how to use this data, please consult our "Using the Atlas" page.
| Files | GIS Files +AK/HI |
KMZ Files -AK/HI |
KMZ Files +AK/HI |
|---|---|---|---|
| Full file Not generalized | 503 MB | N/A | N/A |
| Generalized .0001 deg. tolerance | 224 MB | N/A | N/A |
| Generalized .001 deg. tolerance | 52 MB | 33 MB | 46 MB |
| Generalized .01 deg. tolerance | 9 MB | 7 MB | 10 MB |
| Generalized .05 deg. tolerance | 4 MB | 5 MB | 5 MB |
| Files | GIS Files +AK/HI |
KMZ Files -AK/HI |
KMZ Files +AK/HI |
|---|---|---|---|
| Full file Not generalized | 110 MB | N/A | N/A |
| Generalized .0001 deg. tolerance | 53 MB | N/A | N/A |
| Generalized .001 deg. tolerance | 14 MB | 7 MB | 10 MB |
| Generalized .01 deg. tolerance | 2 MB | 1 MB | 2 MB |
| Generalized .05 deg. tolerance | .6 MB | .5 MB | 1 MB |
The Full files contain all the detail incorporated in the original state boundary files, and align very closely with the modern county boundaries in Google Earth and ESRI products. However, since the full files are very large, they may not always display rapidly in web applications.
We have therefore created generalized versions of the US historical boundary files. These files contain all of the counties and state/territories included in the full file, along with all of the attribute information. The detail of the boundary lines has been reduced using algorithms incorporated in ESRI software, resulting in a significant reduction in file size. Due to the procedure used, the resulting polygons still fit together exactly at any selected date.
KMZ files for the US are provided both with and without Alaska & Hawaii. The files shown above as Not Available (N/A) were too large for practical use with Google Earth.
The follow chart shows the approximate scale at which the generalization becomes noticeable on map polygons:
| File | Scale |
|---|---|
| Full map | N/A |
| Generalized (.0001 deg. tolerance) | 1:25,000 (1 inch = 0.4 mile) |
| Generalized (.001 deg. tolerance) | 1:250,000 (1 inch = 4 miles) |
| Generalized (.01 deg. tolerance) | 1:2,500,000 (1 inch = 39 miles) |
| Generalized (.05 deg. tolerance) | 1:12,500,000 (1 inch = 197 miles) |
