Use it as a guide. It is an abstract. There are errors. It does not contain every piece of information on the state's copy of the record. VERIFY ALL INFORMATION. Some feel the state database is better than the federal government database at the Bureau of Land Management. They are different. Check both. You can search for a BLM Land Patent at: http://www.glorecords.blm.gov/PatentSearch/. That is also an abstract. There are errors. It does not contain all the information on the federal copy of the record. At this site you can download a copy of the land patent certificate. A genealogist will want to obtain a copy of the land record which includes the underlying documents related to the land purchase. You can find more information on how to order a land record at: http://www.glorecords.blm.gov/Visitors/Requests.asp#nara.
Illinois is a federal lands state. That makes it easier to plot your ancestor's land on a map. You do need to understand townships and sections. If you scroll to the bottom of the Illinois State Archives Database page above there are diagrams of all the information you need.
There is a tract book at courthouse in the Office of the County Clerk. It is the local database. After the courthouse burnt April 15, 1857, the county reconstructed land records from the copy of the record held by the state – the same copy used for the State Archives database. They also asked residents to bring in their deeds and other documents and copied them, by hand, for the record. Thus, despite the fire, the land records exist.
To find your ancestor's neighbors go to the state archives site. Chose search by legal description. Fill in the section number, township number, range number and meridian but no name and you will get a list for the section. On the BLM You can list your search results by several methods. One method is by date of issue. This will tell you who the first settler was, right? Wrong. Unfortunately, the dates may be misleading. For example, in Mt. Pulaski Township, Logan County, the patent for Robert Downing, one of the earliest settlers, is dated March 2, 1933, long after he was dead. The one for George W. Turley, another of the earliest settlers, is dated May 16, 1912. Both of these are certificates that were reissued by the government for some reason.1 Both were originally entered December 1, 1830. You will find, under the December 1, 1830, date, copies of the originally issues certificates issued in both of the above instances with the reissue under the later date. But the date of the land patent is NOT the date your ancestor settled. It is basically the date the paperwork was completed or, in these two cases, the date the paperwork was reissued.
These are the ORIGINAL purchasers of the land from the federal government. This is a work in progress.
This page is "Logan County Original Land Purchasers" on the Logan County, Illinois, ILGenWeb site. The address of this page is http://logan.illinoisgenweb.org/originalbuyer.htm.