Hesse-Darmstadt , German Hesse-Darmstadt , former landgrave, grand duchy and state Germany . It was founded in 1567 in the division of old Hesse; After Hessen-Kassel was taken over by Prussia in 1866, Hessen-Darmstadt was commonly known simply as Hessen.
Hessen-Darmstadt was originally just the small area of the Oberen Katzenelnbogen with Darmstadt, which is in what is today the extreme southern part of today's country Hesse is located. But the Landgraviat received significant territorial gains in the 17th and 18th centuries, in part due to its unwavering loyalty to the Habsburg Holy Roman Emperors. Hesse-Darmstadt entered Napoleon's Rheinbund in 1806 and was therefore elevated to grand duchy status that year. Hesse-Darmstadt joined the Allies in 1813 and 1815 the German Confederation at. The Congress of Vienna Some Hessian-Darmstadt lands were ceded to Prussia and Bavaria, but as compensation the duchy received, among other things, a district on the west bank of the Rhine with the important cities of Mainz and Worms. The Grand Duke Louis I (r. 1768–1830) granted Hesse-Darmstadt a constitution in 1820, implemented other reforms, and made the Grand Duchy became the first southern German state to join the Prussian Customs Union. Hesse-Darmstadt then oscillated between liberalism and conservatism . The Duchy placed itself in Seven Week War (1866) to the side of the Austrians and thus lost its territory north of the Mains to the Prussian-sponsored North German Confederation . But when the German Empire was founded in 1871, Hesse-Darmstadt became one of its constituent States.
After the abdication of the last Grand Duke Ernest Louis , In 1918, Hesse became a republic and one of the constituent states of the Weimar Republic of post-war Germany. In 1945 the area east of the Rhine was in the US occupation zone and became part of the country Hessian (later called simply Hessen), while the rest are part of the country Rhineland-Palatinate.