Wallace Line to the west of the Philippines. Wallace's studies in Indonesia demonstrated the emerging theory of evolution, at about the same time as Joseph Dalton Hooker and Asa Gray published essays also supporting Darwin's hypothesis. Understanding of the biogeography of the region centers on the relationship of ancient sea levels to the continental shelves. Wallace's Line is visible geographically when the continental shelf contours are examined; it can be seen as a deep-water channel that marks the southeastern edge of the Sunda Shelf which links Borneo, Bali, Java, and Sumatra underwater to the mainland of southeastern Asia. Australia is likewise connected
Illinois–Indiana State Line Boundary Marker Illinois–Indiana State Line Boundary Marker The Illinois–Indiana State Line Boundary Marker is a sandstone boundary marker obelisk located near the end of Chicago's Avenue G, just west of the State Line Generating Plant of Hammond, Indiana. Since 1988 it has been north of the Wabash River. The obelisk was constructed by the Office of the United States Surveyor General ca. 1838. In 1988, the marker was relocated north of its original location, but the structure continues to straddle the state line between Illinois and Indiana. As one of the earliest structures still standing in Chicago, the marker earned Chicago Landmark