Does anyone know if there are additional records housed at the National Archives (or any other place) pertaining to the the Federal Land Conveyances?

I'm familiar with the digitized certificates that can be downloaded via the BLM website, however I "heard" that there were additional documents filled out at the time of the purchase that "may" have additional information on the person(s) that purchased land--a type of application.

Any help greatly appreciated.

Lyle