An early Three Sisters theory...

Pioneer geologist ET Hodge suggested in 1925 that these stratovolcanoes were actually the remnants of a single collapsed volcano, a theory since disproved (Fire Mountains of the West. 1988 Mountain Press Publishing Company). His thought was that the broad arc of peaks encompassing Broken Top through Devil's Hill, the Wife, Husband, and little Brother formed the outline of an ancient Caldera rim for the mega-volcano he dubbed Mt Multnomah. As seen from Mary's Peak looking across the Willamette Valley February 2006.