|Class E - States of the United States||Washington|
|Works related to Washington, a state of the United States; not to be confused with Washington, D.C., a city, and capital of the United States.|
- “Washington (territory)” by J. W. Hawes in The American Cyclopædia, 1879.
- “Washington (territory)” by T. W. Symons in Encyclopædia Britannica (9th ed.), 1888.
- “Washington” in The Nuttall Encyclopædia by James Wood, London: Frederick Warne and Co., Ltd., 1907.
- “State of Washington,” by W. J. Metz in Catholic Encyclopedia, 1913.
- “Washington (State),” Collier's New Encyclopedia. New York: P.F. Collier & Son Co., 1921.
- Edmond Stephen Meaney, “Washington (State),” Encyclopædia Britannica (12th ed.), 1922.