USS Constitution is a grounded ship that is being occupied by friendly robots. There is one of the most interesting side quests connected with it and inside, you find lots of interesting items.
As soon as you come closer, a robot will fly up to you and he starts a conversation. It starts quest Last voyage of the U.S.S. Constitution .
It is best to explore the ship after, or towards the end of, the quest that you receive from the robot - Last voyage of the U.S.S. Constitution. If you choose to side with scavengers, do this after you complete this quest. If you decide to side with the robots, do this after you restore power to the ship's engines.
If you side with the robots, you need to keep in mind that you will have to leave behind the majority of loot from the ship, because any attempt to take them will be considered a theft. Therefore, if its caps that you are after, side with scavengers.
In the captain's room that is secured with a master lock, there are, among others, a lot of meds, ammo, power armor gun, cash, and also U.S. Covert Operations Manual on the table.