Some of the filming took place at Prairie Grove Battlefield State Park in Arkansas. The film crew built a false side onto one of the historic buildings there and then blew it off for a special effect - assuring the State park officials that no harm would come to the building. The explosion was rather larger than promised and caused some damage to the structure of the historic house.
One of Gregory Peck's greatest heroes from childhood was President Abraham Lincoln. Peck was initially concerned about playing him since at 66 he was a decade older than Lincoln was when he was assassinated.