Just this June 2008, I visited Plains, MT, and discovered the book "Horse Plains: Montana Territory" 1984, by Maurice Helterline (pronounced 'Morris'). Mr. Helterline has gleaned vintage Plains info from all the local sources. His book is a delightful read. I recommend it! I even found one entry for my family, Courser/Corser, and with his indexes, I found several of my ancestors in the Plains cemetery. We bought the last hard copy (sorry) that the museum had in Thompson Falls.

However, I also saw an updated soft copy version at the Sanders County Courthouse Vital Records Department along with two volumes of indexes. You can order copies by contacting The Printery, P.O. Box 988, Plains, MT 59859, at 1-800-926-4513 or 406-826-3605.
http://www.the-printery.net/index.html

Mr. Helterline's cemetery indexes are also online here:
http://www.rootsweb.ancestry.com/~mtsander/cemeteries.htm

Maurice is a difficult man to reach. The Missoulian has a charming write-up on him along with his photo here:
http://www.missoulian.com/articles/2005/04/16/hometowns/ht01...

I recommend calling the Printery directly. Hope that helps everyone. Enjoy...

Deb