It should be narrow enough that it can be researched thoroughly in the time available. It should be significant.
Librarians are usually very helpful people.
If students can't find a published work in the library, they may get it through inter-library loan. The state archives is located in Olympia. There are regional archives in Seattle and at Eastern Washington University, Central Washington University, and Western Washington University. Sandpoint Way NE, Seattle, WA 98115. The NA-PNW has material bearing on national subjects.