In prehistoric times the lands of the canton were inhabited by people of the Pfyn culture along the lake. During Roman times the canton was part of the province "Raetia" until in 450 the lands were settled by the Alamanni. It was only in the 8th century that the canton became a political unit similar to what it is known today, as a Gau of the Frankish Empire. At the time, however, the area was not so clearly defined and changed frequently. Overall, the size of the Thurgau was larger, but during the Middle Ages the canton became smaller in size. The dukes of Zähringen and the counts of Kyburg took over much of the land.