It is estimated that over 40% of the current United States population is descended from immigrants that passed through Ellis Island. Tracing your genealogy to these immigrants can sometimes be difficult.
Your first step is gathering information on the immigrants in your genealogy. Ask family members where the family came from and about when they came to the US. In some cases, you may get lucky and find a family member that has the naturalization papers where the ancestor applied for citizenship.
Census records are often helpful as well. In many censuses, individuals were asked the year the immigrated (or how long they've been in the US), whether they are naturalized, and the year of naturalization.
Once you've gathered as much information as possible, it's time to search Ellis Island records. When searching the immigration records, it is important to keep in mind that the spelling of names are often different. The person taking the information may have used a spelling that they assumed was correct or the individual passing through Ellis Island may have Anglicized their name.
Don't be surprised if you find several immigrants with the same name. It may be necessary to narrow your results by the age of the immigrant, their country of emigration, their nationality, where they were going, or who they were traveling with.