Friday, July 16, 2010

Exploring Newberry's Atlas of Historical County Boundaries

The Newberry Library Genealogy News Blog announced the Completion of Digital Atlas of Historical County Boundaries - "a dataset that covers every day-to-day change in the size, shape, location, name, organization, and attachment of each U.S. county and state from the creation of the first county in 1634 through 2000."

Read the entire blog post for more details. I clicked on the link to the Atlas of Historical County Boundaries ( and saw:

The site does not permit clicking on a state in the map area. You have to pick from the dropdown menu on the right, or pick from the list of states, to pick a state.

I picked California from the "Interactive Map" dropdown menu, and saw:

There is a menu ribbon on the left of the map - with icons for View (to toggle overview map in upper left corner), Zoom In, Zoom Out, Full (zoom in to full extent), Back (go back one screen), Pan (use the "magic hand" to move the map image around), Link, Info, Query, Measure, Select by Rectangle, Select by Line/Polygon, Clear and Print. You click on the icon, and then do the action on the map.

In the upper right corner is a date box - to see the historical map boundaries for any date, you have to enter the date in this box and click on the "Refresh" button. The default date is the first set of boundaries available. For California, that was 18 February 1850.

Further down on the right side of the screen is a list of "layers." You can select any number of layers to be visible, but only one is "active."

There are links at the bottom of the page for "Chronologies," "Supplemental Texts," "County Index," Select a State, and "Home."

I used the Zoom In tool and the Pan tool to look at Southern California as of 18 February 1850:

I changed the date to 18 February 1900, and selected all but the "Unsuccessful Proposals" layer to be visible, and only "Modern County Seats" to be "active," and saw:

By clicking on the "Chronologies" link at the bottom, the user can see a list of all of the county historical boundary changes described by date, additions to and subtractions from which other counties, etc., plus a reference for each change. Here's the California list:

As on most websites, the Help page is your friend. For this site, reading the Help page will shortcut your trial and error searches on this site. The Help page is here:

I haven't explored some of the more complex features of the site. I see that, in the "Downbload GIS files" on the home page, that the user can download files for each state in GIS, KMZ (Google Earth) or PDF formats.

The graphical user interface with icons on the left side of the map is fairly clunky, but it works, and has a learning curve - most people should be able to master it in 5 or 10 minutes. The layers feature can provide helpful information.

This type of mapping feature is valuable to researchers, in order to find where their ancestral records might be located (usually in the county at the time the event was recorded). The digital maps may be helpful to determine if someone who lived on the edge of a county was actually in another county at one time or another. Using the digital file with Google Earth may help the researcher understand the terrain when his ancestor resided in a particular place.

1 comment:

Diana Ritchie said...

Hi Randy ~ Thanks for posting this..what a great resource!! One thing - I was able to click on a state from the big map...not sure why it wouldn't let you. I need to explore it some more - great thing to do on a Saturday morning :-)