Anthony W. Robins did not set out to amass one of the most important surviving archives of the original World Trade Center. Though he is an architectural historian devoted to the buildings of New York City, Mr. Robins didn’t even set out to study the twin towers.

Rather, Gale Research, which was planning a series of books in the 1980s under the rubric “Classics of American Architecture,” asked Mr. Robins if he would turn his attention first to the trade center before tackling a monograph on the Chrysler Building, which was his preference.

Mr. Robins, now 62, is a well-known figure in landmarks circles, having served on the staff of the Landmarks Preservation Commission for 19 years. He is an adjunct professor at Columbia University and New York University. And if you happen to see a walking tour coming your way under the confident leadership of a man in a Bailey Dalton safari hat — well, that’s Mr. Robins....