Although presented in digitized format here, all of these publications are available in print format from the WSDOT Library collection.
Development of Washington State Highways and Transportation (pdf 840 kb)
A History of Highways: Washington State Highway & Transportation Commission 1951-1993 - Washington State Highway & Transportation Department 1905-1993
History of Roads & Highways in the State of Washington (pdf 2.6 mb)
An early history of roads in Washington state, from territorial days to the 1930s.
40 Years with the Washington Depart ment of Highways (pdf 104k)
An outline of the growth and development of the Washington Department of Highways from its creation in 1905 to the close of World War II in 1945.
History of Floating Bridges in the State of Washington (pdf 561k) A brief overview of floating bridges in Washington through the late eighties.
Identification of State Highways (December 1, 1965)
Includes two tables; one converting Legislative highway numbers to corresponding SR numbers, and the other converting SR numbers to corresponding Legislative highway numbers.
State Roads as Established by the Legislature, 1893-1935 (pdf 1.3 MB)
An atlas of 19 maps, illustrating the roads established by law in each legislative session. Note that not all of these roads were built.
Available from the Washington State Library
Historical Washington maps, including highway maps from 1909, 1912, 1915, 1931, 1933, 1939, and 1950.
WSU Libraries Digital Collections - Early Washington Maps