NORTH AMERICA/Continental Interior 35 Figure 16 Cross section of typical ‘plains type fold’ (Slick Carson oil field, T32S, R3E, Cowley County, Kansas) Note the anticline closure increases with depth, faulted on east flank, and temperature high over crest of anticline; all characteristics of oil producing plains type folds on the Santa Fe and Oregon trails on their way west used it for lubricating their wagon wheels Petroleum was discovered in a well drilled in 1860 near Paola, Kansas, opening the large Midcontinent Oil and Gas Province shortly after the Drake well was drilled in 1859 in Pennsylvania Natural gas was exploited for town lighting, starting in about 1870 Gold discoveries in the Black Hills of South Dakota and in the Rocky Mountains in Colorado spurred the gold rushes, with thousands of get-rich