A map dealer who specialized in finding elusive treasures for rich collectors admitted in federal court on Thursday to having stolen 97 antique maps worth more than $3 million from more than a half-dozen universities and libraries over the last seven and a half years.

One of the hardest-hit institutions was the New York Public Library, which lost 32 maps, but rare book collections in Boston, Chicago and London were also victims, according to federal prosecutors.

The admissions by the map dealer, Edward Forbes Smiley III, came roughly one year after he was caught with five rare maps in his briefcase and tweed jacket minutes after leaving Yale University's rare-book library. A video surveillance system showed him removing a map valued at $150,000 from a book.