(CNN) -- Researchers have made an unexpected discovery among the items a member of the Donner Party kept in a carpetbag on the group's ill-fated journey to California: a military document with Abraham Lincoln's handwriting on it.
Donner Party member James Reed and his family carried muster rolls with Lincoln's name on them among their treasured heirlooms, the Abraham Lincoln Presidential Library and Museum said in a statement released Monday.
A team of librarians, historians and handwriting experts combined forces to confirm that Lincoln's writing was on one of the documents, which list Lincoln and volunteer soldiers who fought in the 1832 Black Hawk War.
"We often find documents that detail fascinating stories about Abraham Lincoln's life and times, but it is rare indeed for the document to have such an intriguing history after it was written," said Daniel Stowell, director of the Papers of Abraham Lincoln. "That these documents detail part of Lincoln's military service and that they accompanied the Donner Party to California makes them doubly significant."
All four of the muster rolls include "Private Abraham Lincoln" among the list of soldiers. On one of them, experts say two-and-a-half lines are clearly written in Lincoln's hand. And the documents reveal that Lincoln had a horse worth $85 and equipment valued at $15, noting that Lincoln received one tent that was United States property to be returned at the end of his service.
The lines Lincoln wrote said: "Muster Roll of Captain Jacob M. Earleys Company of Mounted Volunteers Mustered out of the service of the United States By order of Brigadier General Atkinson of the United States army on White Water Rivers of Rock River on the 10th day of July 1832."
The documents are part of the James Frazier Reed Collection at the California State Library.
Reed's name appears just beneath Lincoln's on the list. He was one of the organizing members of the Donner Party, the group of pioneers known for resorting to cannibalism while enduring a harsh winter in the Sierra Nevada mountains.
He likely inherited the papers from the military company's commander and took them with him when he left Springfield, Illinois, in April 1846 because they were part of his personal history, the Lincoln Presidential Library said.
While historians believe the papers accompanied the Donner Party for their entire journey, Reed did not. He was banished from the group after fighting with a teamster and stabbing him to death, Monday's library statement said.
He left the papers with his wife after being expelled from the party, and "she brought them safely in her bosom to California when helped by the first relief party which went to their assistance," daughter Martha Jane "Patty" Reed recalled.