United Baltic Duchy ended in 1918.
Duchy of Savoy ended in 1713.
The Grand Duchy of Moscow.
A duchy is the jurisdiction of a Duke. You'd have to check out the specific duchy for more detailed information. A good place to start is the British Royalty website.
The Baltic Sea.
Since the first duke of England was the Duke of Cornwall, the son of Edward III, 1337, I'm going to assume that the first Duchy would be the same, Duchy of Cornwall. The Duchy of Lancaster is held by the Soverign. in Lancaster the toast, "To the Queen, Duke of Lancaster" that's "Duke" not Duchess.
United Baltic Duchy was created in 1918.
Duchy of Württemberg ended in 1806.
Duchy of Neopatria ended in 1390.
Duchy of Zator ended in 1919.
Duchy of Silesia ended in 1918.
Duchy of Limburg ended in 1794.
Duchy of Salzburg ended in 1918.
Duchy of Ferrara ended in 1597.
Duchy of Holstein ended in 1866.
Duchy of Jülich ended in 1815.
Duchy of Bar ended in 1766.
Duchy of Schleswig ended in 1866.