This book records transactions where the U.S. Government (agents) was the Grantor. Some early settlers walked into the Land Office and made a purchase. For others, they were given a tract of land in payment for their service in the United States Armed Forces.
These Land Grants transactions are indexed by location ie. Range and Township. http://www.glorecords.blm.gov/search/default.aspx
These records may be found on-line by going to The Bureau of Land Management (BLM). They may be downloaded and printed.