The website for the Northwestern Digital Archives includes collections from Idaho, Montana, Oregon, Alaska, and Washington. As with any online catalog, various church record collections can be found. A search using the keyword "church" brought back over 2,000 results.
I encourage you to search this catalog for church records for your Northwestern ancestor. Here are a few examples of what you can find.
Guide to the Scandinavian Lutheran Church Records 1890-1965
Guide to the Methodist Church Collection 1848-1979
Guide to the Congregational Church Collection 1848-1986
Guide to the Luther Memorial Lutheran Church Records 1891-2003
Guide to the Seattle First Baptist Church Records 1869-2006
Guide to the Vancouver Avenue First Baptist Church Collection 1940-2011
Guide to the Episcopal Church Collection 1830-2010
Guide to the First Presbyterian Church (Seattle, WA) Records 1873-1996
