As railroads expanded westward across the united states in the late-1800s, native americans were increasingly unable to hunt across the formerly open landscape of the great plains. in addition to the problems stated here, what other issue contributed to the problems faced by native americans on the great plains at the end of the 19th century? a) european diseases wiped out a substantial portion of the sioux population. b) timber land was harvested, robbing native americans of a valuable resource. c) under the dawes act, indian reservations lost all of their federal funding. d) railroads brought an increase in population, leading to controversies over land usage.