Is Islam a religion? And What events and figures have shaped the development of Islam in the United States?

Yes, Islam is a Religion. Here is an overview - and variety of articles re Islam in the US:
http://usinfo.state.gov/products/pubs/muslimlife/

And tons more here:
http://www.google.com/search?hl=en&q=%22islam+in+the+united+states%22&btnG=Google+Search