Wallace Line by the Sahul Shelf to New Guinea. The biogeographic boundary known as Lydekker's Line, which separates the eastern edge of Wallacea from the Australian region, has a similar origin to the Wallace line. During ice age glacial advances, when the , both Asia and Australia were united with what are now islands on their respective continental shelves as continuous land masses, but the deep water between those two large continental shelf areas was, for over 50 million years, a barrier that kept the flora and fauna of Australia separated from those of Asia. Wallacea consists of islands that were not
Wallace, Idaho the Montana state line. East of Wallace, the "Route of the Hiawatha" (rails-to-trails) and the Lookout Pass ski area are popular with locals and tourists. Wallace came into being on a river plain where four streams and five canyons converge onto the course of the South Fork. The earliest known white interest in the area was the construction of the Mullan Road, which followed the South Fork from near Cataldo almost to the pass that crossed into Montana. John Mullan did observe promising quartz outcroppings along their route when he passed through in late 1859. However, he later frankly stated