The present has a way of changing the way that historians think about the past. The trauma of Sept. 11, 2001, is likely to be no exception: Five years after the attacks on New York and Washington, many historians say 9/11 and its aftermath are leaving their mark on how American history is written and taught.

American history is being studied less as the story of a neatly packaged nation state and more in a global context, as part of something much larger, many historians say. The idea of America as an empire, too, is in vogue. And historians are giving new attention to topics like the turbulent history of civil liberties in the United States.

There is growing interest in the history of terrorism, of Muslims in America, of international cultural conflicts and exchanges. The history of foreign policy is being rethought, some historians said, with less emphasis on the cold war and more on post-colonial politics. The Iranian revolution and the hostage crisis from 1979 to 1981 seem like significant turning points in ways that they had not before.

“For historians, history is never set in stone,” said Joanne Meyerowitz, a professor of history and American studies at Yale who edited “History and September 11th” (Temple University Press, 2003), a collection of essays. “It’s written and rewritten in each generation. The events of the present, of the contemporary age, always help us reframe the events of the past. And the events of the past always help us to reframe the age we’re living in.”