Mainz-Kastel is a district of the city Wiesbaden, which is the capital of the German state Hesse in western Germany.
Kastel is the historical bridgehead of Mainz, the capital of the German state Rhineland-Palatinate and is located on the right side of the Rhine river. Kastel faces the historical center of Mainz and the two cities are connected by a road bridge. Kastel is located about one kilometer below today's water mouth of the river Main into the Rhine.
In its long history Kastel repeatedly belonged to Mainz and was formally incorporated on 1 April 1908. Since Mainz was part of the French occupation zone (formed after World War II) and Kastel was part of the American occupation zone, the Americans ordained that Kastel should be part of the administration of Wiesbaden. Ever since 25 July 1945, Kastel belongs to the Hessian state capital Wiesbaden.
The newly formed German federal states adapted the boundaries of the occupation zones. Therefore, Kastel is a district of Wiesbaden and part of the German state Hesse. Kastel is one of six districts of Mainz on the right-hand side of the Rhine which were separated from Mainz in this way. The separation from Mainz is the issue of intense debates by local patriots in three districts (Kastel, Amöneburg and Kostheim). Many Kastel residents feel like they belong to Mainz which reflects, apart from the administrative affiliation, the reality of everyday life. The city center of Wiesbaden is about ten kilometers from Kastel whereas the city center of Mainz is just on the opposite side of the Rhine. The three mentioned districts of Wiesbaden still bear the designation "Mainz- ..." because until today no closed formal legal act has been made up. The signs, when entering the districts, are a curiosity because they say "Federal State Capital Wiesbaden District Mainz-Kastel". On the other hand, many inhabitants of Kastel feel like they belong to the German state Hesse (Mainz was a part of the Grand Duchy of Hesse from 1815-World War II) and do not identify with Rhineland-Palatinate whatsoever.
Adolphus Busch, founder of Anheuser-Busch, was born in Kastel (now Mainz-Kastel) in 1839.
CB&I Lummus operated an office in Mainz-Kastel which has been bought by Alstom as of 30 October 2009.