Lighthouses are, by their nature, each unique. So, choosing three, and calling them a unique group is a bit of a difficult task.
Each of the three I've chosen for this page does, however, have something that sets it apart.
One, in New Jersey, is the oldest surviving working lighthouse in the United States. Another, on one of South Carolina's barrier islands, was the last manned lighthouse to be built on U.S. soil. In Oregon, they built one on one of the most dangerous locations of any in the country, and, after decommissioning, it served a rather different purpose.
They're not necessarily uniquely American, as appearances mark just one of them as such. What makes each different probably does not do so from a global perspective, either. But, each one has at least one quality that makes it unique among those lights found in the United States.
Here, then are brief stories of what it is that makes the beacons at Sandy Hook, Tillamook Rock, and Sullivan's Island unique.