The Free State of Prussia (Freistaat Preussen) was a German state formed in the aftermath of World War I. It was the major state of Germany during the time of the Weimar Republic, comprising almost five-eighths of its territory and population. "Free State" is a German term for Republic. The democratic Free State of Prussia was taken over by coup in 1933 and its President Otto von Braun taken out of office. His government went to court over this ouster and after the end of war, Otto von Braun approached U.S. officials to reinstate the legal Prussian government. They and the other Allied Occupation forces, who had taken up occupation of all of Germany, were not interested and declared Prussia abolished in 1947.

In the last part of the 19th century, hundreds of small Germanic kingdoms, princedoms, duchies, margravates, etc., were finally united into the German Empire (Deutsches Reich). The more important units became Länder (states); others became Provinzen (provinces) within the states. At the end of World War I, the portions of Posen and West Prussia provinces remaining in Germany merged to form the Posen-West Prussia Frontier province (Provinz Grenzmark Posen-Westpreußen).

The flag was divided into three horizontal stripes and in half vertically. (horizontal stripes: first row: black-white, second row: white-black, third row: black-white). The flag was adopted in 1920 and abolished in 1935 by the Third Reich.

This design is of a possible administrative flag for the Posen-East Prussia Province between 1920-1935, with a coat of arms, consisting of a silver field with a black Prussian eagle; emerging from the neck is a silver arm with armor grasping a silver sword.

The Ostrowska Republic (Republic of Ostrów), which only lasted between October 10, 1918, and November 26, 1918, was another short-lived republic that existed in the former Grand Duchy of Posen. About a month before the start of the Greater Poland Uprising (Powstanie Wielkopolskie), which would bring the whole area out of German hands and back into Poland in 1919, the citizens of the town of Ostrów Wielkopolski decided to liberate themselves from the Germans and declared themselves the independent Ostrowska Republic. This flag, very obviously an ancester of the modern flag of Poland, did fly over an independent Republic of Ostrów for that very short period of time.

Prussia no longer exists as an independent state, but is split into two parts and incorporated into the modern countries of Germany and Poland. The Polish flag dates back to the pennants of the Middle Ages. At first they were all red with a white eagle, but by the 17th Century the background colors of red and white stripes were firmly established. The banners usually bore the official crest of the State. These Polish national colors were used during the November Uprising of 1831, and the colors were used in all national uprisings since that time. They were officially recognized as state colors in 1919 after Poland had regained her independence.

Poland's "landesfarben," or land colors, derived from its coat-of-arms, are white-red; the opposite of the red-white of modern Brandenburg (West Prussia), which is now located in Germany. The State Flag of Poland, with the Polish coat-of-arms, has been in use since 1919. The flags only change came during Communist rule when the crown was removed from the head of the eagle. After Poland became independant the crown was returned. Interestingly, Poland doesn't have a king, but the crown remains. Some also claim the length of the eagle's claws having been changed.

Although this is an early Third Reich flag, it seemed better suited at this location since individual State flags virtually disappeared in Germany after 1935. This was the Flag of the Free State of Prussia during its brief existence in the Nazi era.

One of the results of the disappearence of the Free State of Prussia was the forming of the "Landsmannschaft Ostpreussen" (Territorial Association of East Prussia) as a non-profit organization for Germans who were evacuated or expelled from East Prussia during World War II and its aftermath. It was formed in 1948 by a group of East Prussian "vertriebene" (refugees) in West Germany. The Landsmannschaft of East Prussia flies a hanging flag (Banner) in the historical East Prussian colors of black and white. Instead of the historical coat-of-arms of East Prussia, they use the arms of the Landsmannschaft, an elk's antler.