In order that the fullest record possible be kept of the expedition, captains Lewis and Clark required their sergeants to keep journals to compensate for possible loss of the captains’ own accounts. The sergeants’ accounts extend and corroborate the journals of Lewis and Clark and contribute to the full record of the expedition. Volume 10 contains the journal of expedition member Sergeant Patrick Gass.
Gass was promoted to sergeant on the expedition to fill the place of the deceased Charles Floyd. His journal was subsequently published and proved quite popular: it went through six editions in six years. A skilled carpenter, Gass was almost certainly responsible for supervising the building of Forts Mandan and Clatsop; his records of those forts are particularly detailed and useful. Gass was to live until 1870, the last survivor of the expedition and the one who lived to see transcontinental communication fulfill the promise of the expedition.