The letters consist of thirteen letters, eleven written by George W. Featherstonhaugh to Col. John J. Abert and two written by Thomas Fitzpatrick to Lt. James W. Abert. The letters relate to geological findings, land explorations, and dealings with Native Americans. The letters written by George W. Featherstonhaugh from various locales (such as Detroit, Green Bay, Prairie du Chien, North Carolina, and Quebec) for the most part detail his explorations; geological reports; descriptions of flora, fauna, and the people encountered; and difficulties with terrain and conditions. The letters written by Thomas Fitzpatrick from St. Louis detail his findings on Native American languages, political news, and gossip.