Ken,
This is about the best I could find on him, he married a Chickasaw abt 1850-Mary Ann Cheadle she was my Gm.prior marriage-
-John Johnston was a slave holder and opened a large farm on the South Canadian just prior to the Civil War.
He moved to the Blue and died there -in (1866).---[His wf died in 1877}
This was stated from his son bio-- Douglas H Johnston--O'Briene or Leader's and Leading Men ?

He had been a land speculalor in Mississippi,this was in Mississippian/Ala area a wealthy-powerful family name-before 1800 into statehood Ala 1819 on into removal period.