Amajor problem created by the rapid growth of american cities in the late 19th century was a) discarding mass amount of human and consumer waste. b) living in close proximity to large livestock and horses. c) inventing modes of communication in densely populated cities. d) finding ways of building tall buildings in tight urban spaces. 21) in approximately what decade did the urban population surpass the rural population in the united states? a) 1900s b) 1910s c) 1920s d) 1930s 22) the most important result of the spanish american war was that it a) spread democracy to latin america. b) secured a safe source of raw materials for us industry. c) guaranteed the independence of mexico from spanish control. eliminate d) set up a colonial empire for the u. s. and set the u. s. on the road to empire.