Over fifty Civil War letters of Perry Mayo, written to his family in Calhoun County, Michigan, from June 1861 to May 1864, constitute the bulk of this collection. They include vivid descriptions of battles, marches, military personnel and camp life, together with observations on the conduct of the war.

Also in this collection are numerous and fragmentary attempts at genealogy, with related correspondence which, in addition to Mayo, include such family names as Angell, Bryant, Carpenter, Coryell, Freytag, and Price. A published volume relating to the Price family of Barrett Township, Monroe County, Pennsylvania is also included. There is a folder of transcribed letters dated 1885-1888.

There are also documents relating to the history of Michigan State University and to the Michigan State Grange, in which the Mayos were active participants. Photographs include portraits of Perry Mayo, his wife, Mary, and other family members.

Finally, there are letters of recommendation for Nelson S. Mayo, who was apparently removed from his position at Kansas State Agricultural College for political reasons.