Rheingau and the Wine Business
The Rheingau is a wine region since approximately the 11th century, when monks brought the wine making business into the region. It was mainly the Benedictine (Kloster Johannisberg) and the Cistercian monks (Kloster Eberbach) who made the business so important and successful for the Rheingau. Having the Rhine right in front of the door was also a great advantage for the business in terms of transportation.
When you visit the area, you see references to this quite often, like this painting I found in a wine tavern.