 A major development in the second half of the 19th century was a rapid expansion of paleontology in North America.In 1858 Joseph Leidy described a "Hadrosaurus" skeleton, which was the first North American dinosaur to be described from good remains.However, it was the massive westward expansion of railroads, military bases, and settlements into Kansas and other parts of the Western United States following the American Civil War that really fueled the expansion of fossil collection.