mission from Philip I, Landgrave of Hesse. In 1567, upon Philip�s death, the Landgraviate of Hesse was divided among his four sons. His youngest son, Philip II, Landgrave of Hesse-Rheinfels, was awarded the Lower County of Katzenelnbogen, and thereby the castle and the town. In 1580, 175 people in Sankt Goar fell victim to the Plague; only 18 years later, in 1598, it claimed another 142. In 1635, in the midst of the Thirty Years' War, more than 200 people died in another outbreak. In 1598, Franz Schmoll built the Rheinfels-Apotheke in Sankt Goar, only the third apothecary in Hesse, after the ones in Kassel and Marburg.
As a result of a longstanding dispute between Hesse-Kassel and Hesse-Darmstadt over the partitioning of the Landgraviate of Hesse, the latter had Burg Rheinfels and Sankt Goar besieged for several weeks in the summer of 1626 with help from Imperial troops. which eventually led to the town�s capitulation and its attendant plundering by Spanish troops. Between 1626 and 1647, Sankt Goar belonged to Hesse-Darmstadt. In 1647, troops of Landgravine Amalie Elisabeth of Hesse-Kassel conquered the castle and the town. On 14 April 1648, George II, Landgrave of Hesse-Darmstadt ceded the Lower County of Katzenelnbogen along with Sankt Goar �in perpetuity� to Hesse-Kassel.
While Hesse-Kassel was under Imperial law the rightful landholder, lordship over the Lower County of Katzenelnbogen passed to Landgrave Ernst I, who on 30 March 1649 made his entrance into Sankt Goar and founded the Hesse-Rheinfels(-Rotenburg) line. Landgrave Ernst ruled until his death in 1693 at Burg Rheinfels, his comital residence, as one who was tolerant in matters of religion, and one who took great interest in his office, contributing considerably to Sankt Goar�s economic growth, something the town sorely needed after the ravages that it had sustained in the Thirty Years� War. In the Nine Years' War (known in Germany as the Pf�lzischer Erbfolgekrieg, or War of the Palatine
