The two latest finds – a 19th-century illustrated text of the Mississippi River by Henry Lewis and a 17th-century French book on the Louisiana territory by Louis Hennepin – were purchased from Ketterer in 1998 by Stephan Loewentheil, a Baltimore book dealer who had no idea that they were stolen. Mr. Loewentheil had sold the books, but bought them back after learning about the theft in order to return them to the library, said Howard Spiegler, a New York lawyer whose firm represents the Swedish library. The pair are worth about $255,000, Mr. Spiegler said.
The Hennepin contains the first published description of Niagara Falls and the first published panorama of the Louisiana Territory. Thomas Jefferson once owned a copy, which helped interest him in purchasing the region from France in 1803. The Swedish library has been adding a collection of every item printed in the country – from a Bible to a bus schedule – since 1661.