This place is a hidden gem on Nantucket. Off the beaten path a bit, yes. But worth the walk. The restaurant is bustling but not too loud, the service was impecable and the food was outstanding -- not to mention unbelievably affordable! We had the most amazing mussels for an appetizer and the waitress (thoughtfully) brought us extra bread to sop up the mouthwatering broth. The oysters were top notch as well. We also had a salmon special that was out of this world. The tripe on the menu was good but completely overshadowed by the special. Too full for dessert, we happily walked off what we could on the 4 or 5 block walk back to Main Street. I highly recommend Fifty-Six Union. A great, overall experience.