When I worked as a genealogy reference librarian, researchers often came to the desk with an old land record and wanted to know the exact location of the land their ancestor purchased. This was usually a bit of a pain, as it involved finding a map of the particular state showing the townships, ranges and sections.
But I just discovered a handy online tool from Earthpoint that makes the process much easier. It takes a land description and maps it on Google Earth.
So, for example, I found a General Land Office record from 1825 showing that James Gillespie purchased a particular piece of land in Stark County, Ohio.
Specifically, he purchased land in Section 26 of Township 17-N and Range 6-W, based on the Ohio River meridian.
I entered this information into the Township and Range search tool on Earthpoint:
Then I clicked the "Fly on to Google Earth" button. (This only works if you've installed Google Earth on your computer.) The program then creates a KLM file that opens automatically on Google Earth. It marks the location of Section 26, Township 17N and Range 6W with a purple boundry:
Going back to the original land record, I see that James Gillespie's land was the western half of the southwest corner of Section 26; so it was approximately the area I've circled here: