Lillie, Found burial for Margaret Helen DAWSON at Morris Hill Cemetery, Boise. Buried 3 December 1918, family burial no mortuary. Buried Section B, Block 73, Lot 1. Didn't find anyone else there, I think you need to look at Canyon county cemeteries.
You need to look at the Western States Marriage Index. If you need I will post link. Curious about where you came up with 3rd marriage to Virgin? I found a marriage for Emily Virgin DAWSON is why I ask. Unusual name .
Have you ever had research done thru Idaho State Historical & Genealogical Library??