On December 1, 1978, its historic district was recognized and placed on the National Register of Historic Places. The City of Waterloo also has been recognized for its work through Sister Cities International. On October 2, 1980, Waterloo announced a Sister Cities partnership (officially recognized April 1981) with Porta Westfalica in (then) West Germany. Due primarily to the efforts of Vera Kohlmeier of Waterloo and Helmut Macke of Porta Westfalica, it came about as a result of genealogical research, which concluded that perhaps two-thirds of Monroe County's German population could trace their ancestry back to this region of northern Germany.Porta Westfalica itself came about in 1973 as a conglomeration of 15 villages into a city of over 40,000. Located on the Weser River in northern Germany, Porta Westfalica is situated in a valley between two large hills. Trips by large groups typically occur every two years, including visits by the Waterloo German Band and the Bläserkreis, Porta's 70-member youth brass band. Charitable donations have also been raised for East German refugees and the victims of the 1993 flood. This partnership, which goes by the portmanteau Portaloo, has since assisted other communities in the area to establish Sister Cities programs of their own, including Columbia/Gedern, Belleville/Paderborn, and Millstadt/Groß-Bieberau. "Portaloo" has been honored with seven coveted Readers Digest awards for its Sister Cities program. Every summer this city holds it annual "Porta Westfalica Fest" or "PortaFest" in honor of its sister city.