Wash the peanuts in cool water until the water runs clear. Soak in cool water for 30 minutes to loosen any remaining dirt.
Drain and rinse the peanuts. Add the peanuts to a 12-quart pot along with the salt and 3 gallons of water. Stir well. Cover and cook on high for 4 hours. Check the texture of the peanut at this point for doneness. When done, boiled peanuts should have a similar texture to a cooked dry bean. It should hold its shape, but not crunch when bitten. Add more water throughout the cooking process, if needed. If necessary, continue cooking for 3 to 4 hours longer.
Drain the peanuts and store in a covered container in the refrigerator for up to 1 week.
*Cook's note: The cooking time can vary greatly depending on how fresh the peanuts are. The fresher the peanut, the less time it will take to cook.