Contains census, election, and vital statistics data for 118 British and Irish counties for the period 1851 to 1966. The information was collected for use in a study of regional integration and development in Great Britain in the 19th and 20th centuries. Included are population indicators for each of the counties recorded at 11 points in time during the 115-year span (i.e., 1851, 1861, 1871, 1881, 1891, 1901, 1911, 1921, 1931, 1951, and 1961). Specific information includes indicators of population density and change, ethnic composition, proportion of election votes for Labour, Conservative, Liberal, and various nationalist parties, and proportion of population employed in areas such as agriculture, manufacturing, civil service, and (female) domestic work. Other data include number of Celtic speakers, literacy, religiosity, nativity (i.e., English-, Welsh-, Scottish-, Irish-, and French-born), sex ratio (female to male), birth rates, infant mortality rates, marriage rates, per capita income, and proportion of middle class.