25 November 2012

Does Ancestry.com Know About Decimals?

[this issue has been corrected as of 4 January 2013--see update]

[minor editing of this post at 12:15 PM central on 25 November]

Decimals matter. If you're not certain, ask your bank. They mattered to your ancestor too, especially if he bought and sold real estate.

The first screen shot in this blog post is of the results page for Clark Sargent's entry in the Illinois, Public Land Purchase Records, 1800-1990 database at Ancestry.com.

I thought that the price, total [paid], and acreage looked a little strange. First of all the price [per acre] and the acreage do not compute with the stated acreage of 4000 acres. It's also true that 4000 acres would encompass more than one section in a given Winnebago County township [sections are usually 640 acres]. Something is not right with these numbers.

This is a database that Ancestry.com pulled from another source--which is fine. The State of Illinois (actually the Illinois State Archives) maintains the website on which the state version of the database is maintained. Ancestry.com's "Source Information" is shown below.

Searching for Clark on the Illinois State Archives website's version of the database (titled: Illinois Public Domain Land Tract Sales) confirmed what I expected: the numbers on Ancestry.com were wrong.

There are decimals in the numbers that appeared to be "off." The acreage is 40.00 acres, the price is $1.25 an acre and the total price is $50.00. Those numbers all make more sense than the ones at Ancestry.com.

I guessed that this error did not just happen for Clark. I was right--the search results page at Ancestry.com's database showed the following for another person of interest: Andrew Trask.

Sure enough, those entries had the missing decimals in price, total, and acreage.

I use this database on the Illinois State Archives website regularly and rarely use it at Ancestry.com.  Otherwise I might have noticed it easier.


  • Look at the original.
  • Never assume an index is correct.
  • Check the numbers to see if they "make sense."
Errors like this actually concern me on several levels. If something as simple as decimals can't be transferred over correctly, what else might be a little "off?"

All these search results screens are accurate as of 25 November 2012--1:00 AM CST.

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