* The Iroquois and Their Western Neighbors, 1650–1730 (University of Nebraska Press, 1981)
* The Treaties of Utrecht and Rastatt (Cambridge University Press, 1957)
* Origins and Growth of American Diplomacy, 1775–1895 (Knopf, 1959)
* New York: Past and Present (Prentice-Hall, 1968)
* Wisconsin: A History (Meredith, 1968)
* Connecticut: A Bicentennial History (W.W. Norton, 1976)
* The Federal Union: A History of the United States to 1865 (Prentice-Hall, 1978)
* America's History (Scott, Foresman, 1984)
* The Life of Thomas E. Dewey (Twayne, 1984)
* The United States: A Documentary History (Holt, Rinehart and Winston, 1989)
Articles
* "The Iroquois and the Diplomacy of the American Revolution," New York History (1958)
* "The Impact of the American Revolution on the British Empire," Journal of American History (1960)
* "Connecticut's Role in the American Revolution," Connecticut Historical Society Bulletin (1976)
* "Thomas E. Dewey and the Republican Party," American Historical Review (1984)
* "The United States in World War II," U.S. News & World Report (1991)
Other Works
* Editor of the American Historical Review (1972-1978)
* President of the Organization of American Historians (1979-1980)
* Editor-in-Chief of the Encyclopedia of American Foreign Relations (1997)