We present an analysis of the overall publishing landscape in the period 1500-1800 based on comprehensive harmonization and joint analysis of four large bibliographic catalogs. This has allowed us to assess publishing activity beyond what is accessible by the use of national catalogs alone. In addition to the historical analysis of knowledge production trends, we are releasing the openly licensed source code for catalog harmonization, and a notable improved version of the Finnish national bibliography, Fennica. This code and data release demonstrate the potential of our approach for research use of library catalogs, and the essential role that data harmonization and integration plays in this process.