Before 100 BC Celts lived in the area. Later the Franks came into this area as graves from the 7th century prove. The first written document is the "Life" of the first bishop of Münster. It describes how bishop Ludger walked from Budica, now Büttgen, through the forest of Hamrithi. The earliest known written mention of Kaarst refers to it as 'Karlesforst' and dates back to 1218. Karl was a very common name for frankish nobles including king Charlemagne ('Karl der Große'), but a link between Charlemagne and Kaarst has not been proven.