When it comes to sour cherries - the Montmorency is the king. It is the most common sour cherry grown in the US. Most of them are grown in Michigan, but also Door County in Wisconsin is known for them. They are named after a valley in France. Their color is a beautiful bright red on the outside and white in the middle. Most of these cherries end up in pies and jams. If you are buying a pie filling in the store, it's most likely going to be made of Montmorency. You may also see that name pop up in the juice aisle.
In recent years, there has been a lot of attention placed on drinking tart cherry juice, for it's many health benefits. These cherries are an antioxidant that contain vitamin A, vitamin B6, and beta carotene. I have also heard of people drinking some everyday to help with muscle pain and inflammation. You can buy the juice ready to drink or you can buy concentrate that you add water to.
As it comes to taste, Montmorency pack a lot of flavor. They are sour, but not to the point of say a lemon. My 3 year old daughter ate them right off the tree. I made some delicious cherry sorbet with some Montmorency cherries that I picked myself.