Passenger Lists are important records for tracing your immigrant ancestor. Most immigrants before the mid 1900s came to the United States on ships and there are some records remaining of lists of passengers on those ships, especially in the 18th and 19 centuries. Passenger lists usually included the passenger name, place of origin, birth date, departure date, arrival date, and the ship name. Depending on the year your ancestor came to the United States and the county they came from, you may be able to find a passenger list for your some of your ancestors.
Herrick District Library has many books of passenger lists from different European countries. Some of the more well known books are Germans to America, Dutch Immigrants in U.S. Ship Passenger Manifests (Netherlands), and The Famine Immigrants (Ireland). There is also a large list of books at Herrick Library in our Genealogy Department covering emigration and immigration. Some of these books contain passenger lists. Some do not contain actual passenger lists but have names of immigrants coming to the U.S.
In addition to the many books covering emigration and immigration at Herrick District Library, there are also some microfilm reels of passenger lists of ships arriving in New York. The years covered are mainly 1845-1854. There is no index to these reels, so you would need to know the approximate date they emigrated.
There are also websites with passenger lists, including Ellis Island and Castle Garden. Ancestry Library Edition has a large amount of passenger lists, and Family Search is another great place to look.
As always, feel free to ask at the Information Desk for help!