A letter to President Abraham Lincoln from three military surgeons requesting a chaplain to tend to the wounded and dying soldiers after the Battle of Antietam, accompanied by the president's signed response, were returned to the National Archives on Thursday.

Bill Panagopulos, president of Alexander Historical Auctions, in Stamford, Conn., helped negotiate the return and handed the documents over to David Ferriero, archivist of the United States, at a ceremony at the National Archives.

Investigative archivist Mitchell Yockelson spotted the letters in a New York dealer's catalog of rare items in 2009. The documents may have been taken while still in the custody of the War Department before they ever became part of the Archives' collection of billions of documents, officials said....