Thank You for the reply and recommendations. I have found some additional info on my great grandfather August Carlsson.
I did find him in the 1880 Census of Deuel Co, Dakota Territories. I also fond a website about the history of Gary South Dakota.http://www.experiencegarysd.com/gary-historical-assn.cfm
There was an online copy of the book "Gary, South Dakota Gate City to the Dakotas 1872 - 1972" On pg 6 it make several reference about him, including that in 1878 he was appointed Postmaster at Gary. He also opened the 1st permanent store in Gary in 1877.
It also contained a big surprise for me (and my dad as well.) Apparently August was married more than once.It indicated his wife died January 4th 1878 and was the 1st white death in Gary.
My dad has his grandfathers original marriage certificate. It states he married Celestia May Martin on January 31 1897 in Herrick Deuel Co., Dakota Territory. And Celestia is listed as his wife on the 1880 Deuel Co Census.
So now the 64 thousand dollar question is who was this wife referenced in the Gary book?
I'll check out the references you listed to see if I can find the answer there.