Duchy of Krnov was created in 1437.
A republic is a form of government which is not rules and aristocrat: a king (monarchy), prince (principate) or duke (duchy). a republic can have any king of political regime, so long as it is not rules by an aristocrat. It can be a democracy, an authoritarian state or a dictatorship. Most modern countries are republics.
Originally, dukes were men in the Roman army who had achieved the rank of general, but could not hold it because they were not Roman citizens by birth. Early in the Middle Ages, the title was pretty much interchangeable with the title of general. It quickly became a term for a man who controlled a large piece of territory and maintained a powerful fighting force. In this capacity, it was a title of nobility, higher than count or earl. By the time of the High Middle Ages, it was the highest title of nobility, though it was below that of any royal rank, such as prince. In some places, dukes were monarchs in their own right. As such they were often called archdukes. Monarchs whose ranks were of nobility rather than monarchy were prone to deciding they were kings, however.
MasterCard was created in 1966.
The Carpathians was created in 1988.
The Western was created in 1970.
Duchy of Krnov ended in 1623.
Krnov was created in 1221.
Duchy of Racibórz was created in 1172.
Duchy of Silesia was created in 1163.
Duchy of Westphalia was created in 1180.
Duchy of Bielsko was created in 1572.
Duchy of Głubczyce was created in 1172.
Duchy of Zator was created in 1454.
Duchy of Limburg was created in 1065.
Duchy of Friuli was created in 569.
Duchy of Żagań was created in 1274.
Duchy of Württemberg was created in 1495.