What did the historian Frederick Jackson Turner argue about the importance of the western frontier in American history in 1893? Why did the U.S. government decide to move Indians to reservations around the mid-nineteenth century? Why did the Plains Indians sign the Treaty of Fort Laramie, which ceded some of their land to allow the passage of wagon trains? Which group or groups decimated the buffalo herds on the Great Plains in the late nineteenth century? What was the outcome of the second Treaty of Fort Laramie? Which of the following describes the state of the Native American population in the continental United States by 1900? What occurred under the "outing system" of the 1880s? What was the outcome of the Dawes Act of 1887? Who was Geronimo?