He has published three books on the diplomatic history of the early American republic: The American Union and the Problem of Neighborhood: The United States and the Collapse of the Spanish Empire, 1783-1829 (University of North Carolina Press, 1998); John Quincy Adams: Policymaker for the Union (SR Books, 2001); and The Louisiana Purchase: Jefferson’s Noble Bargain? (Thomas Jefferson Foundation, 2003). He also served as a consultant and writer for the Black Hawk War section of "Lincoln/Net," a website of the Abraham Lincoln Historical Digitization Project at Northern Illinois University. He is currently completing a book on the Aaron Burr conspiracy.