A large part of the county was transferred to the Commonwealth to make the Australian Capital Territory in 1909, with the remaining part the area to the north-west of the ACT as far north as the Burrinjuck Dam, and thin strips of land along the western, southern and south-eastern borders of the ACT.
In 1909, a significant part of the county was transferred to the Commonwealth to create the Australian Capital Territory. The remaining area, extending from north-western regions up to the Burrinjuck Dam and including narrow strips along the western, southern, and southeastern borders of the ACT, remained.