Whenever the boundaries of any organized county shall have been enlarged by the addition thereto of any additional territory, the board of county commissioners of such county shall redistrict the county into commissioner districts immediately. Such redistricting may be done at a regular or special meeting. The districts shall be made as regular and as compact in form as practicable and as nearly equal in population as possible, but no new district shall be so formed that any two of the then acting commissioners shall reside in the same district.