The following is a summary of acts which authorized boundary changes for Johnson County.
- Acts of 1837-38, Chapter 211, authorized the Johnson County Court to hire some suitable person to run the lines between Johnson and Carter counties and to return a fair plat of such line to the Johnson County Court.
- Acts of 1851-52, Chapter 249, changed the boundary between Carter and Johnson counties so as to include in Carter County the tracts of land on which Joshua Perkins and Richard G. Perkins lived.
- Private Acts of 1911, Chapter 275, changed the county line between Johnson and Carter counties so as to include all the lands of I. W. McQueen and V.A.S. Rainbolt in Johnson County.