Explore historical and current immigration issues by locating books. Try searching using an event (potato famine), ethnic or immigrant group (Irish immigrants), etc.
Try a keyword search. Use similar searches inserting another country name, ethnic or immigrant group:
Check these websites for information regarding why people immigrated.
U.S. Citizenship and Immigration Services: http://www.uscis.gov/portal/site/uscis
PBS Teachers: http://www.pbs.org/teachers/
Choose a grade range, then Social Studies, and Filter resources by: Topic (Immigration or other relevant topic)
About.com: Immigration Issues:
Internet Public Library:
Use the search term "immigration"