The letter was written Dec. 3, 1864, by Morgan W. Carter. It is the only known document in which an African- American soldier describes an important Civil War battle, said Wyatt Houston Day, who initiated the auction. Day told The Indianapolis Star that other letters might have been written, but this is the first he has seen in 30 years.
"If I haven't seen something, it has to be pretty scarce," Day said.
Day estimates the letter is worth $6,000 to $8,000 but said it could fetch nearly double that at the auction.
"He writes beautifully," Day said.
Carter's letter is in good condition, written on "wove paper" in ink that has mostly held up. The letter features some misspellings that speak to Carter's likely lack of formal education, but Day said it doesn't detract from its poignant descriptions of the effects of the battle on soldiers.
Jefferson County historian Janice Barnes said Carter and his father and brother are well-documented in county historical records to a point, but then the trail runs cold.
Morgan Carter was mustered out of the Army in Corpus Christi, Texas, and returned to Madison, where he worked for his father, but there are no records for him after that.
Barnes said it's unclear if Carter has any descendants. The historical society, which has been researching the Carter family, has not been able to find evidence of a marriage, children or census records after the Civil War for Carter.
His brother, John Carter Jr., was a teacher in Switzerland and Jefferson counties, but there is no evidence he had children, either.
Barnes said she would love for the historical society to be able to acquire the letter but doesn't think that's likely.
"Right now, we're kind of strapped for cash," she said.
Still, she's glad to know about it.
"It puts a little more blood and bones on the few facts we've been able to gather," Barnes said.
Day said he hopes a museum or institution wins the auction for the letter so it can be seen by the public.
"I would not like it to go to a private collector," Day said. "It would go underground again."