In the mid to late 30's in Germany, there was a lot of work done in creating vehicles with a low Cd. The impetous for this was the building of the Autobahn, which provided a roadway that was capable of handling much higher speeds than the typical car/engine combinations available at the time could produce. They soon found that by reducing a car's drag, the existing engines could propel a car much faster down the Autobahn than it could could do in a traditionally shaped car body. Unfortunately this bout of automotive experimentation was shut down with the the start of WWII and most of the vehicles lost in the ensuing conflict. The following website (in Germen) shows a number of these cars (hit the "Tour" buttom at the bottom of each page to go to the next page). Its interesting to look at the state of the art back in the 1930's. There were some fairly wild looking designs.
1939 Maybach Stromlinienkarosserie