What do you do with these maps? 

 

First visit Illinois Public Domain Land Sales  (LaSalle is county 50 here) 

OR the BLM Land Patent Grants

Jot down the Township, Range and Section number then come back here to our map page.  For instance - My husbands GGG - Grandfather (George Billings) lived at Township 35 (T35N), Range 2E (R2E), Section 16.  Now I find the point where T35N & R2E intersect (Ophir Township), view the plat map for that section and walla, that little square with a number 16 on it in Ophir Township is the section where my husbands ancestors lived in 1850!!