Is there anyway to get a complete list of all the general stores you can sell your stuff at? Or is there a way to find them in-game? If anyone knows a list of the stores with locations, that would be much appreciated!
New York: Rhinelander's Sugars - Very southern end of New York, there are two fast travel points. Just south of the center one you will find the store.
There are two other stores, but neither are conveniently near a fast travel point and will be very hard to accurately describe. One is west and slightly north of the dead center of New York. The other is one block back from the water on the east coast. About 2 blocks south of where the buildings end and the farmland begins. Sorry, best I can do.
There are also roaming peddler wagons. I've seen one in the Frontier and one in Boston, but they only sell consumables (bullets, arrows etc).