A post office called "Rockdale" was established 106 years ago in 1912, and remained in operation until 1915. The community in the Cascade Range was named for the abundance of rock near the original town site. Just south of Snoqualmie Pass, it was at the west portal of the Snoqualmie Tunnel, constructed by the Chicago, Milwaukee, St. Paul and Pacific Railroad (The Milwaukee Road) from 1912 to 1914.
- U.S. Geological Survey Geographic Names Information System: Rockdale, Washington
- "Post Offices". Jim Forte Postal History. Retrieved 22 August 2016.
- Meany, Edmond S. (1923). Origin of Washington geographic names. Seattle: University of Washington Press. p. 246.
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