Is there a lighthouse near Liberty Island?

Obviously, I'm not from NY. I was recently one of the dreaded 'tourist' that New Yorkers hate to see coming :). While riding the Staten Island Ferry I noticed what looks like a small lighthouse in the harbor. it's quite small, & sits on the island by itself...actually, I'm not even sure it's an island, it could almost be a manmade structure. I took pictures, but haven't uploaded them yet. I tried to look it up to find out whether or not it actually is, but every time I do a search for lighthouses in that area the only thing I come up with is the Statue of Liberty. Does anyone know?