Phyllis, Ardmore is in Carter County.Perhaps if you posted a query on the Carter County, Oklahoma message board you could find someone who was familiar with your PASSMOREs.Here's a link to the message board:
Lastly, this is a link to a webpage about Indian Territory and Oklahoma Territory resources.Before statehood in 1907, Oklahoma was divided into territories containing land belonging to several tribal nations.Non-Indians were considered "intruders" (the official name) in Indian Territory and had to have permission to live there.So what you refer to as a "reservation" was actually a separate and distinct nation.
As the land belonging to the tribes was gradually (and vastly) decreased by the U.S. Government, "allotments" were set aside for some Indian nations. Perhaps your ancestors received an allotment?Many citizens of the tribal nations refused allotments (for many reasons) and many refused to have their names put on the Government's lists or "rolls."(This makes research difficult for those of us who descend from full-bloods who refused admission to the "rolls."But I find our ancestors had other things in mind than preserving careful records for their genealogist off-spring descendants!:o))