In a large skillet cook the bacon for 2-3 minutes. Add in the beef and onion and cook until the meat is no longer pink, then drain.
Combine the beef mixture, bacon, beans, brown sugar, ketchup, vinegar, mustard and salt in a slow cooker.
For the slow cooker, you can cook on high for 3-4 hours, or low for 6-8 hours. If you are cooking on high be prepared for stirring it once in a while in case your crockpot runs hot. The beans can burn on the edges if you have a really hot slow cooker.
Serve and enjoy!
Nutrition is an automatic estimate and will vary with the brands you use.
Recipe from https://fastandslowcooking.com/crockpot-calico-beans/