When Lewis and Clark came through southwest Montana in 1805, they named many rivers — but if they referred to the mountain ranges by name, the names are not recorded. The 1865 DeLacey Map of Montana Territory does not name the Tobacco Roots. The first written reference to the mountains between the Madison and Jefferson Rivers is F.V. Hayden's 6th Annual Report of the Geological Surveys of the Territories for 1873, in which the name South Bowlder Range is mentioned, a reference to the largest river in the north part of the mountains. Although this usage (usually spelled "South Boulder Range") is followed in many Geographies and Atlases of the 1890s and early 1900s, the USGS Three Forks Folio Peale, A.C., 1896, Three Forks Folio, U.S. Geological Survey labels the mountains "Jefferson Range."
