George S. Patton is important in United States history because he played an important role in defeating Germany during the Second World War.  

Patton's was best known in WWII for commanding tanks in North Africa, in Sicily, and eventually in the invasion of Normandy.  His use of tanks made him one of the most important American generals and the general who was most respected and feared by the Germans.  The fact that the Germans felt this way about him worked to the Allies' advantage.  They tricked the Germans into believing the D-Day invasion would come at the Pas de Calais rather than in Normandy.  They did so by placing Patton in command of a fictional force that was supposedly based in the area of England across from Calais.  The Germans assumed that Patton would lead the invasion force and therefore fell for this trick.