The Concord Point light sits in a park in Havre de Grace, right at the mouth of the Susquehanna river. The light was built in 1827 and the sign outside it proclaims that the light is the "oldest lighthouse in continuous operation in the U.S." I think they mean on the Chesapeake Bay.
The lighthouse was manned by the O'Neill family until 1928; it is now automated. John O'Neill was the first lightkeeper - he was granted the position for his heroic defense of Havre de Grace against the British during the War of 1812. On May 3, 1813, he manned the guns singlehandedly until his capture.
The lighthouse is on the National Register of Historic Places.
Peeking in through the keyhole in the door, I could see that the steps are concrete and spiral to the top of the light. I would estimate that the light is about 40-50 feet in height and the walls appear to be made of brick, painted white.
The Susquehanna river travels 444 miles from the north to reach the bay at this point.
Directions: take 95 to route 155 into Havre de Grace. Turn left on to Otaego Street; turn right onto Union Avenue; turn left onto Lafayette Street.