The William P. Nicholls Files contain extensive records of his work for the Copper Range Company and his role in local and state organizations. This includes correspondence and reports, as well as large chronological files.

For his files pertaining to the Copper Range Railroad Company, see the records of the President's Office in Series IX, Subseries IV.

Also note that this subseries overlaps with the Land Department and Lands and Forestry Division Records (Series II, Subseries VIII).