It's a bit off the beaten path, although you'll see signs directing you there. It's certainly worth the trip if you are interested in island history.
Built in a refurbished 1905 stone building, the museum is very well done. There are artifacts and displays showing the islands history, but the most engaging story is told in the video they show. It's quite long (about 45 minutes) and you may not sit through the whole thing, but it tells the story of the old days through the time when the US Navy took over the island and up until the present day. Most of the speaking is from elderly island natives and each has a remarkable story.
After all of the great beaches, guest houses, restaurants, and fun, take an hour or two to get some insight on the history of the unique island of Culebra. It will be time well spent.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.