Don Homuth, of Salem, Ore., says the map was given to him by his eighth-grade teacher. It was created by Orlando Ferguson of Hot Springs, S.D.
Homuth used to live in Fargo and was a North Dakota state senator.
Library of Congress spokesman Robert Morris told The Forum newspaper that officials checked more than 75 maps before confirming the design was one-of-a-kind.
He says the only other known copy of the map is in the Pioneer Museum in Hot Springs.
