### Early History and Indigenous Peoples Long before the concept of Germany existed, the area now known as Hesse was inhabited by Celtic tribes. By the time the Roman Empire expanded to the Rhine, the primary inhabitants were the Chatti, a Germanic tribe whose name eventually evolved linguistically into "Hesse." The Romans built the *Limes Germanicus* (a fortified border) through the Taunus mountains to keep the Chatti and other tribes at bay.
### Medieval Era and the Reformation During the early Middle Ages, the region became part of the Frankish Empire. The historical roots of the modern state trace back to the Landgraviate of Hesse, which emerged in the 13th century. Hesse played a profound role in the Protestant Reformation. Under Philip the Magnanimous in the 16th century, Hesse was an early champion of Protestantism, famously hosting the Marburg Colloquy in 1529 in an attempt to unify Protestant leaders Martin Luther and Huldrych Zwingli.
### Fragmentation and 19th Century Following Philip's death, the territory was divided among his sons, leading to centuries of fragmented Hessian states, most notably Hesse-Kassel (which later became an Electorate) and Hesse-Darmstadt (which became a Grand Duchy). Hesse-Kassel became famous in American history for providing "Hessian" mercenary soldiers to the British during the American Revolutionary War. In 1866, following the Austro-Prussian War, Prussia annexed Hesse-Kassel, Nassau, and the Free City of Frankfurt, forming the Prussian Province of Hesse-Nassau, while Hesse-Darmstadt retained its independence until the end of the German Empire in 1918.
### Modern History The modern boundaries of Hesse were drawn in the aftermath of World War II. On September 19, 1945, the American military administration merged the former Prussian territories of Hesse-Nassau with the People's State of Hesse (formerly Hesse-Darmstadt) to create the new state of Greater Hesse (*Groß-Hessen*), which formally dropped the "Greater" to become simply Hesse in 1946. Following WWII, Hesse experienced a massive influx of refugees and displaced persons, spurring rapid economic development and helping transform Frankfurt into West Germany's financial capital.
