We compare the structure and intrusive history of the West Mageik Lake sill complex to possible conduits for magma transport during the 1912 eruption at the nearby Valley of Ten Thousand Smokes (VTTS), on the Alaska Penninsula, to shed light on some of the enigmatic aspects of the 1912 eruption, including its unusual feeder system and eruptive sequence. At West Mageik Lake, Late Tertiary (?) rhyolitic magma propagated along a roughly easy-west trend as sills that followed bedding planes and through-going joint sets in the Jurassic Naknek siltsone. This demonstrates the feasibility of arc-parallel transport of rhyolitic magma as sills at shallow crustal levels. ¿American Geophysical Union 1991