Flag of Germany
When Heinrich XI, Prince Reuss of Greiz was appointed by Joseph II, Holy Roman Emperor to rule the then-new Principality of Reuss-Greiz on 12 May 1778, the flag adopted by the "Fürstentum Reuß-Greiz" was the first-ever appearance of the black-red-gold tricolour in its modern arrangement in any sovereign state within what today comprises Germany – the Reuss elder line that ruled the principality used a flag whose proportions were close to a "nearly square"-shape 4:5 hoist/fly ratio, instead of the modern German flag's 3:5 figure.
Flag of Germany
West of the Oder–Neisse line, the German states were reorganised along the lines of the zones of occupation, and new state governments were established. Within the American zone, the northern halves of the former states of Württemberg and Baden were merged to form Württemberg-Baden in 1946. As its flag, Württemberg-Baden adopted the black-red-gold tricolour. The choice of these colours was not based on the historical use of the tricolour, but the simple addition of gold to Württemberg's colours of red and black. Coincidentally, Baden's colours were red and yellow, so the colour choice could be mistaken for a combination of the two flags. In 1952, Württemberg-Baden became part of the modern German state of Baden-Württemberg, whose flag is black and gold.