We visited this area from the New Jersey side the day before our trip to New York.
The ferry ride was nice and peaceful and allowed for some great skyline pictures of New York City. The view on the New Jersey side is amazing, even on a drizzly Sunday morning.
We took the first stop to Ellis Island. This museum contained so much history about those who passed through here into the United States. The museum and exhibits are both interesting and enjoyable, and you might just learn a thing or two. Within the museum were exhibits about how immigration breaks out by country, time period, men vs. women, etc., as well as what those immigrants had with them or how they dressed.
Also within the complex is a library where you can search for relatives who may have passed through Ellis Island. For a minimal fee, you can use their computer system to find out any information. My wife was lucky enough to find her great grandfather, the boat he travelled, his actual signature in the manifest, and information about him. It was amazing to see that this histroy was right here, and it was so personal for her.
we also took a quick trip by the Statue of Liberty (we did not stop, as the kids were getting a little restless). The ferry boat moves around the statue before docking to allow for some great pictures of Ms. Liberty.