Notes:
https://www.familysearch.org/en/wiki/W%C3%BCrttemberg,_German_Empire_Genealogy
From FamilySearch Wiki:
The Kingdom of Württemberg (German: Königreich Württemberg) was a German state that existed from 1805 to 1918, located within the area that is now Baden-Württemberg. The kingdom was a continuation of the Duchy of Württemberg, which existed from 1495 to 1805. Prior to 1495, Württemberg was a County in the former Duchy of Swabia (Schwaben).
As Germany underwent violent revolution near the end of World War I, the Kingdom of Württemberg was transformed from a monarchy to a democratic republic (the Free People's State of Württemberg) without bloodshed; its borders and internal administration remained unchanged. In 1933, Württemberg and all other German states were abolished, in spirit if not in law. It was merged briefly into the "gau" of Württemberg-Hohenzollern. After World War II, Württemberg was split between the US and French Allied Occupation Zones in Germany and became parts of two new states: Württemberg-Baden (run by the Americans) and a smaller Württemberg-Hohenzollern (run by the French.)
These two states were merged with Baden in 1952 to form the modern German state of Baden-Württemberg.