Two small lighthouses, one in front of the other, built in 1873 to guide vessels in from the Atlantic across the Merrimack bar — line one up directly above the other from your foredeck and you were in the channel. The cast-iron front-range light is 14 feet tall; the rear-range light, set back two blocks, is 53 feet.
The lights were decommissioned in the 1960s but both have been preserved and the rear-range light is occasionally open for climbs through the Friends of Newburyport Harbor Lighthouses. Look for them at the end of Water Street.