High German is a somewhat different language than Low German, rather than a dialect. I am not really sure of the classification, but it always seemed to me that Low German is closer to Dutch, Frisian, or English.
In Ohio, Low German is spoken by the Mennonite religious group, and a dialect of High German called Pennsylvania Dutch. These languages tend not to be grammatically correct like a textbook and have a lot of local flavor, depending on the region. I think it is called 'low' due to the fact that the region in W. Europe is low land, but I can't be sure about that. Pennsylvania 'Dutch' is a mispronunciation of the word Deitsch, the name of the German dialect for the German language (Pfälzisch dialect/Palatine dialect). It is the first language for many Amish and Lutherans, as well as Mennonites, and in many parts of Ohio and Pennsylvania is used more frequently than English. However, many people go back and forth between Low German, High German, Pennsylvania Dutch, and English in everyday speech.
My mom's family came from Saxony (Sachsen) for centuries and Jitschin (Jičín) before that, so I was required to learn some German growing up, but it is a very hard language for me and my memory of it is bad. I do much better with Slavic languages or languages from India (Indo-Aryan termed by linguists). This is in terms of confidence level in speaking. To make it more complicated, my relatives from Saxony often enjoyed traveling extensively in the 50s and 60s from East Germany to other countries and back, and they liked South America a lot (according to family lore), eventually ending up there. So Spanish can be added to the list, lol. I think that they enjoyed Germany quite a lot and life there, and we are planning to meet the relatives at some point in the near future.