An ancient tribe known as the Chatti Melibokus may have stayed on a high hill in the Bergstraße region of Hesse (the part that lies south), in Germany.

[1][2] One Diether I (c. 1065–1095) of Katzenelnbogen (literally, 'cat's elbow'), then serving as Vogt of Prüm Abbey, was first mentioned about 1070 in a deed issued by Archbishop Anno II of Cologne.

The War of the Katzenelnbogen Succession was a long, drawn out legal and military conflict over inheritance from 1500 until 1557 between the Landgraviate of Hesse and the County of Nassau-Siegen.

With the formation of the Confederation of the Rhine in 1806, the County of Katzenelnbogen was annexed to the French Empire as the first of its trans-Rhine territories, and this was held until the overthrow of Emperor Napoleon I in 1814.

The whole county was reunited in 1402 by Johann IV, son of Diether VIII, who had married his cousin Anna, daughter and heiress of Eberhard V, in 1385.