If you are one of the approximately three people on the planet currently enjoying this treasure trove of obscure history, you might ask where it all came from. With some exceptions, the answer is Google.
Specifically, Google led me to Newspapers.com, which by good fortune contains many years of the Freeport, Illinois newspaper archives. The old newspapers often published real estate transactions, which helped link our property's chain of ownership. The society pages of these newspapers also told the stories of some of the owners and their families. Newspapers.com can be searched by words, which is a huge help in tracking down names and places. Not all newspapers are included in these online archives, however. For example, the Rockford Register-Star maintains its own subscription-only archives, which are not available anywhere else. Some of the information we found in the Rockford newspaper was important in tracing certain facts and events.
U.S. Census records also helped trace who lived in our house and when they were here. Most census records from 1940 and earlier have been digitized. The original pages that each enumerator filled out as they counted the population can be viewed online either directly from the U.S. Census website, or through third parties like Ancestry.com or Farmilysearch.org. It does take some understanding of how the population was counted, but the information is there. The only exception is the 1890 census, of which very few records remain because of a fire in the building where the records were housed.
Findagrave.com was also valuable in linking family members, as well as dates of birth and death. With the help of genealogists like Richard Hufford, I found pictures of the Hufford family on the findagrave.com website.
I also bought a few Stephenson County plat books on eBay, which helped establish a general outline of who owned our property. These books are fairly accurate in mapping out land ownership, but they are not always 100% correct. Which brings me to a type of very accurate information that (so far) is not available online: the Stephenson County recorder's office. I made a few trips to the recorders office to search the real estate records, which was a bit time consuming, but extremely interesting. My time in the recorder's office confirmed the information I gathered from online sources, and it filled in some gaps in ownership. And the nice people in the recorder's office were very helpful and courteous.
There are some limitations to the information sources, however. Some of the digitized newspaper print is fuzzy enough that the search technology won't detect the right words you're searching for. Also, certain time periods weren't available on the newspaper archive website. The recorder's office had a few pages out of place in some of their index books, which would have been unfortunate if those were the pages I was looking for. The census information is mostly free, but takes some time to navigate if you don't subscribe to one of the services that has indexed the records. Also, census information is only as good as the enumerator who took down the information. For example, Samuel Warn was listed as Samuel Warren in the 1900 census. And you may find the information you're looking for on a census page that looks like this: