|Class E - States of the United States||Colorado|
|Works related to Colorado, a state of the United States.|
- "Physical Features of the Colorado Valley I", by J. W. Powell in Popular Science Monthly Volume 7, August 1875
- "Physical Features of the Colorado Valley II", by J. W. Powell in Popular Science Monthly Volume 7, September 1875
- "The Colorado Desert", by Joseph Francis James in Popular Science Monthly Volume 20, January 1882
- "Colorado for Invalids", by Samuel Augustus Fisk in Popular Science Monthly Volume 25, July 1884
- Olden Times in Colorado by Carlyle Channing Davis, published 1916.
- Field Notes of Junius Henderson (1905-1931)
- Remember Ludlow!, 1914 by Julia May Courtney
- “Colorado” in Encyclopædia Britannica (9th ed.), 1878.
- “Colorado (territory)” by J. W. Hawes in The American Cyclopædia, 1879
- “Colorado” in The Nuttall Encyclopædia by James Wood, London: Frederick Warne and Co., Ltd., 1907.
- “Colorado” in Encyclopædia Britannica, (11th ed.), 1911
- “Colorado,” by Robert S. Morrison in Catholic Encyclopedia, 1913.
- “Colorado,” Collier's New Encyclopedia. New York: P.F. Collier & Son Co., 1921.
- Clyde Augustus Duniway, “Colorado,” Encyclopædia Britannica (12th ed.), 1922.