I think this F M Monks I am talking about may be the same Monks Mahlon Erickson is looking for.
I will give you a little more info. Maybe we can compare birth and death dates.
Francis Marion Monks
Born 31 March 1838
Married to Lucinda
Looks like most of his children were born in the Choctaw Nation Oklahoma
Maybe the reason Monks was turned down for his pension was because he served in the Ark State Guard After the Civil War