Facts and Events
There are 2 vital records available on MyHeritage for Mariann Harkness, including birth records, marriage records, and death records. Vital records are historical records that are typically recorded around the actual time of the event, which means they are likely accurate. Vital records include information like the event date and place, and the person's occupation and residence. Vital records also often include information about the person's relatives. For example, birth and marriage records include names of parents and divorce records list the names of children.
As best as I can transcribe:
1850 US Census, Raisin Twp, Lenawee Co, MI
1860 US Census, Coldwater, Branch Co, MI
It is difficult to tell exactly what the name is supposed to be. Mariann seems like a high probability.
In 1870, there is a single girl, Marian Harkness, age 22, living in the household of Geo. Holden and family, a Stock Dealer in Adrian, Lenawee Co, MI.
There is also a Marian Schofield, age 24, wife of Freeman W. Schofield on Jackson County, MI, which is only interesting because of the following.
In online records for Branch Co., there is a marriage record for a Mariam/Marian V Harkness and Alonzo E Schofield on Nov 11, 1880.