The Demographic Data Base (DDB) produces and makes population databases available for research. The primary sources digitized are parish registers from the 18th and 19th century, but also parish statistics from the period 1749-1859 have been recorded and made available in a database. These historical sources have a proven high quality and contain an amazing amount of information about the Swedish population, which is suitable for studies with a longitudinal and broad perspective. However, the DDB is not only working with historical material and producing databases with historical information. In close collaboration with Statistics Sweden DDB is developing a new infrastructure where historical data is being liked with modern population registers.