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 former NP line was abandoned and removed between St. Regis and Mullan in 1980. Union Pacific continued operating the Wallace-Mullan segment of the NP line until abandoning the entire Plummer-Mullan route in 1992. After abandonment, this segment of former UP and NP lines was developed into the Trail of the Coeur d'Alenes. This trail runs from east of Mullan, through Wallace, to the Washington-Idaho state line west of Plummer. Several miles to the south, the Chicago, Milwaukee, St. Paul and Pacific Railroad, commonly called the Milwaukee Road, ran transcontinental passenger trains between Chicago and Seattle from 1911 to 1961,