River Towns in the Great West: The Structure of Provincial Urbanization in the American West, 1820-1870, by Timothy R. Mahoney and, New Towns in the New World: Images and Perceptions of the Nineteenth-Century Urban Frontier, by David HamerRiver Towns in the Great West: The Structure of Provincial Urbanization in the American West, 1820-1870, by Timothy R. Mahoney. New York, Cambridge University Press, 1990. xi, 319 pp. $39.50 U.S.New Towns in the New World: Images and Perceptions of the Nineteenth-Century Urban Frontier, by David Hamer. New York, Columbia University Press, 1990. ix, 328 pp. $35.00 U.S.