County of Isenburg

Isenburg was a region of Germany located in southern present-day Hesse, located in territories north and south of Frankfurt. The states of Isenburg emerged from the Niederlahngau (located in the Rhineland-Palatinate), which partitioned in 1137 into Isenburg-Isenburg and Isenburg-Limburg-Covern. These countships were partitioned between themselves many times over the next 700 years.

The House of Isenburg was an old aristocratic family of medieval Germany, named after the castle of Isenburg in Rhineland-Palatinate. Occasionally referred to as the House of Rommersdorf before the 12th century, the house originated in the Hessian comitatus of the Niederlahngau in the 10th century. It partitioned into the lines of Isenburg-Isenburg and Isenburg-Limburg-Covern in 1137, before partitioning again into smaller units, but by 1500 only the lines of Isenburg-Büdingen (in Upper Isenburg) and Lower Isenburg remained. In 1664 the Lower Isenburg branch died out. The Büdingen line continued to partition, and by the beginning of the 19th century the lines of Isenburg-Büdingen, Isenburg-Birstein, Isenburg-Meerholz and Isenburg-Wächtersbach existed. Today still exist the (catholic) princes of Isenburg (at Birstein), the (Lutheran) princes of Ysenburg (at Büdingen and Ronneburg) and the (Lutheran) counts of Ysenburg-Philippseich.

Isenburg, the original countship was divided in 1137 into:

It was not until 1806 that there was a state called simply "Isenburg". When the Holy Roman Empire was defeated by Napoleon I of France in that year, the empire was abolished and the Confederation of the Rhine was established amongst the various German states. As an incentive to join the Confederation, it was stated that any state which joined could mediatise their neighbours. Prince Charles of Isenburg-Birstein joined the Confederation and was granted the mediatized Isenburgian Countships of Isenburg-Büdingen, Isenburg-Meerholz, Isenburg-Philippseich, and Isenburg-Wächtersbach. His Principality was renamed to Isenburg.

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