Bee See, you may already have found this page if you have been checking online resources for your question...
Quote:
Under the German Federal Act, the postal systems of the Grand Duchy of Hesse, the duchies of Nassau, Saxe-Weimar, Saxe-Meiningen, and Saxe-Coburg and Gotha, the principalities of Reuss and Schwarzburg-Rudolstadt, the free cities of Frankfurt am Main, Hamburg, Bremen, and Lübeck, the principalities of Hohenzollern-Hechingen, Hohenzollern-Sigmaringen, Lippe-Detmold and Schaumburg-Lippe were placed under the now privately-operated Thurn-und-Taxis-Post. The seat of the post's headquarters in Frankfurt am Main was confirmed on 20 May 1816.
http://en.wikipedia.org/wiki/Thurn-und-Taxis-PostAlso there is a map of the 1843 postal networks in Germany at the website.

Another resource....
http://en.wikipedia.org/wiki/German..._Association