Peasant Republic of Hadeln
The Peasant Republic of Hadeln emerged in the early 13th century on the south bank of the Mouth of the Elbe River under the sovereignty of Saxe-Lauenburg, making it part of Ascanian Germany. Lauenburg proper was well to the east and not contiguous to Hadeln, so Hadeln had the opportunity to be largely self-governing. There were periods during which Hamburg, the Archbishop of Bremen, Denmark or Sweden were dominant, but the Hadeln militia was largely successful in maintaining the republic’s autonomy. The Duke of Lauenburg codified the unique Hadler law in 1543, which is when the database starts. Lauenburg officially remained sovereign over Hadeln until its ruling line died out in 1689.
Although the rest of Lauenburg was then absorbed by Lüneburg-Celle, Hadeln was placed under direct imperial control. That lasted until 1731, when Hadeln was turned over to the Electorate of Hannover (Guelphic Germany), which maintained the tradition of self-governance. I recognize a greater level of autonomy in Hadeln than in principalities absorbed by Hannover by rendering the simplified country name as Hannover-Hadeln. (In other principalities, the simplified country name is just “Hannover”, with the principalities recognized as Landesteile thereof.) Napoleonic forces occupied the territory in 1801, which is when the database ends.
Master list of countries and subdivisions in the Hamburg region