NEW HAVEN, Conn. — A renowned dealer who confessed to stealing nearly 100 rare antique maps should be severely punished because he systematically looted treasures that told the story of the New World and had survived catastrophic events over the centuries, the British Library argued Wednesday.

The maps that E. Forbes Smiley III stole far transcended their estimated value of $3 million, the British Library said in documents filed Wednesday in U.S. District Court.

“The maps stolen by Smiley created the dreams of the explorer, merchant, and powerful,” the library wrote. “They charted the paths of national expansion and empire building. They marked the rise of British dominance, the origins of a new nation, and the demise of a native population. The maps drew the lines between where knowledge ended and imagination began.”

Some of the maps have not been recovered, while others were damaged, the library noted.

“Smiley’s actions ripped at the heart of our public institutions which stored, protected, and made available to the public over centuries – maps, which provided a bridge between past and future generations,” the library wrote.

One of the stolen maps had survived civil war, royal intrigue, economic depression, and the Nazi bombing of London.

“They had been cared for and preserved for centuries until Smiley ripped them from their volumes and slid them into his coat,” the library wrote.

Smiley, a 50-year-old resident of Martha’s Vineyard, faces up to six years in prison under federal guidelines and restitution when he is sentenced on September 27. The British Library is urging the court to impose a higher sentence, citing similar cases in which courts imposed stiff sentences.

Smiley confessed in June that he stole 97 maps over eight years from the New York and Boston public libraries, the Newberry Library in Chicago, the Harvard University library, and the British Library in London. The oldest maps dated back to the 1500s, and some are the first records of settlements, territories, and discoveries in America, experts said.

With Smiley’s help, prosecutors said most of the maps have been recovered from dealers and galleries. Prosecutors said four maps have not been returned by those who have them, and five others are lost.

Smiley’s attorney, Richard Reeve, called the British Library’s arguments “factually and legally flawed.” He said authorities could only prove Smiley stole 18 maps, but his client cooperated with the additional thefts.

“In effect, the libraries are getting back 80 maps that they never would have been able to prove Smiley had taken,” Mr. Reeve said. “He could have sat back and said, ‘Prove it.'”

But that tactic would have exposed Smiley to more prosecutions in other jurisdictions, the attorney for the British Library, Robert Goldman, said.

Smiley was arrested after a Yale librarian found a razor blade on the floor. Yale and other top map libraries reviewed their security procedures after Smiley’s arrest.

The British Library has raised suspicions that Smiley stole additional maps and accused him of “selective cooperation” with authorities. They said prosecutors denied their request to look at Smiley’s statements to them, while Smiley has refused to let them examine whatever records the government may have obtained from him.

Prosecutors said they disagreed with some of the arguments by the British Library but declined to elaborate.

Mr. Reeve said the British Library lacked proof of additional thefts.