Rinse beans well under cool running water. Pick out stones, discolored or misshapen beans and other debris. Put beans in a large pot and fill pot with water, 1-2 inches above the level of the beans. Allow beans to soak over-night.

The next day, drain beans and refill pot with enough fresh water to cover beans by 1-2 inches. Add ham shank to beans. Bring to a boil over high heat. Lower heat so that beans stay at a low boil until tender, 2-3 hours.

Remove ham shank from beans and set aside to cool. Drain beans, reserving two cups cooking liquid. Put beans and reserved cooking liquid in the slow cooker crock. When the ham shank is cool enough to handle, remove meat from bone and chop into small pieces. Add to beans.

In a frying pan, cook bacon just until fat has rendered and bacon is still soft, not crispy. Remove bacon to drain on a plate lined with several layers of paper towels. Reserve two tablespoonsful of bacon grease; discard remainder or save for another use. Cook onions in reserved bacon grease, over medium heat, stirring as needed, until onions are soft. Add garlic and cook for an additional minute. Return drained bacon to the pan with the onions and garlic. Stir together, then add to beans and stir lightly.

In a medium bowl, whisk together the ketchup, brown sugar, maple syrup, mustard and salt. Stir into bean mixture.

Cook on low for 8-10 hours. Stir one or two times during cooking. If needed, add a little water during the last 2-3 hours of cooking. The bean mixture should be loose, but not watery. Turn off slow cooker, stir the beans and allow to sit, covered, for an additional hour. Serve as desired.