NEW YORK, NY October 06, 2006 —On Nine Eleven, New Yorkers spontaneously gathered outside, in public spaces, to comfort one another and honor those who died. People left flowers, candles and handwritten messages. Later, others organized mass plantings of daffodils and trees.

REPORTER: The federal Forest Service has documented more than 700 of these 9/11 "living memorials" nationwide and, with the New School, has created a multimedia exhibit highlighting some of them. Curator Brian McGrath:

MCGRATH: There's a place for the permanent monuments in stone, that weather time. but especially in this event, there was a need for something immediate. And what could be more immediate than planting something, launching a seedling.

REPORTER: McGrath says he was surprised by the places where memorials showed up from tree pits and median strips in the city to the new civic centers of the American suburb.

MCGRATH: People created memorials in office parks, outside shopping malls, schools, campuses.

REPORTER: The exhibit is in Federal Hall, on Wall Street. The historic site is reopening after two years of work to shore up a weak foundation that was made worse by the collapse of the Twin Towers. "Landmarkings - Twelve Journeys through Nine Eleven Living Memorials," runs through October 27th.