Rinse beans and remove any stones. Soak overnight in cold water.
Drain water and cover with fresh water.
Cook on stove till tender, about 1 hour.
Drain water and place beans in crockpot.
Add whole onion or chopped, if you prefer.
Add chunks of salt pork, large enough to remove after cooking.
Add salt, molasses, brown sugar, tomatoes, mustard and vinegar.
Cook at least 4 hours, checking seasoning.
Remove salt pork and onion.