Historians and historical economists have made much progress during the past half century in reconstructing long-term patterns of economic growth. The development of national income accounting techniques provided measures of gross national product and gross national product per capita in both constant and current dollars for the United States and various other countries that extend back to the first half of the nineteenth century. By providing information on the overall performance of the economy and on the performance of its principal industrial sectors and geographic regions, these measures have succinctly characterized the pattern of economic change in the United States, England, France, and several other European nations for periods of up to a century and a half. They have provided a scale against which such developments as urbanization, technological change, and the impact of various governmental policies can be judged. The new information has often led to important reinterpretations of major historical eras. The discovery that the rate of growth of manufacturing declined during the Civil War decade, for example, led to a searching reexamination of the thesis that the Civil War gave an unprecedented impetus to the industrialization of the United States. The disaggregation of the national accounts to the state level produced the unanticipated finding that during the twenty years leading up to the Civil War the South grew at least as rapidly as the North.