One of the most popular ethnic groups in the United States is the Irish. My family includes several lines that trace their lineage back to the Emerald Isle. Irish research can be a real challenge to the average researcher.
Many Irish came to the United States under unique circumstances. In my own lineage I had an ancestor that came to Colonial New England as an indentured servant. The short version of this status is his trip was paid for by someone that he worked for seven years. Upon completion of this he became a full member of early New England society. This would be a trend in Irish immigration to the United States way up into the 1840's. Poor conditions in Ireland forced people to immigrate to the United States.
Here is an excellent link for all things Irish. www.igp-web.com