The plunger pot has a mixed passport. The earliest known patent for one was filed in France in 1852 by Henri-Otto Mayer and Jacques-Victor Delforge. Their press didn't seal against the sides of the pot, so grounds could slip past, and it seems never to have been sold.
The next big step came from Milan. A patent filed in Italy in 1928, and in the U.S. in 1929, was assigned to Attilio Calimani and Giulio Moneta. It described a filter that slid down inside the vessel snugly enough to clear the coffee. The U.S. record names Ugo Paolini as the inventor.
In 1958 the Swiss designer Faliero Bondanini created the version that became the Chambord. Bodum makes the Chambord today. The method itself hasn't changed: steep the grounds, press them down, pour.