I've found a couple of possibilities:
1880 Fahlun, Kandiyohi, MN
August Mattson, b. MN [could be mistake], 23, servant with Magnusen family
1885 Minneapolis, Hennepin, MN
August Matson, b. Sweden, 24
Mary, b. Sweden, 20
1880 Saint Paul, Ramsey, MN
John O. Matson, b. Sweden, 19, laborer, boarder
1885 Saint Paul
Jno Mattson, b. Sweden, 24
I didn't find anything for Bertha.
You might want to contact the Ramsey County Historical Society, St. Paul, www.rchs.com/research
resources.htm. Successful Searching!