The road through the
Clyde Mountain area was surveyed by
Thomas Mitchell in 1855. A
punt service across the Clyde River opened in 1895 and continued until the Nelligen Bridge opened on 12 December 1964. A replacement bridge built by
Seymour Whyte opened in February 2023 with the original demolished. The passing of the
Main Roads Act of 1924 through the
Parliament of New South Wales provided for the declaration of Main Roads, roads partially funded by the State government through the
Main Roads Board (later
Transport for NSW). Main Road No. 51 was declared along this road on 8 August 1928, from the intersection with
Princes Highway at Batemans Bay, via Braidwood, Bungendore, and Queanbeyan to the border with the Federal Capital Territory (today the Australian Capital Territory); to provide for additional declarations of State Highways and Trunk Roads, this was amended to Trunk Road 51 on 8 April 1929. The passing of the
Roads Act of 1993 through the
Parliament of New South Wales updated road classifications and the way they could be declared within New South Wales. Under this act, the highway today retains its declaration as Main Road 51, from the state border with Australian Capital Territory west of Queanbeyan to the intersection with Princes Highway in Batemans Bay. Despite its long-standing classification as a Main Road, and a long historical identity as Kings Highway, the road still has no officially gazetted name.
Transport for NSW has come to an informal agreement with councils along the route to signpost the entire route as Kings Highway. Kings Highway was signed National Route 52 across its entire length in 1974. With the conversion to the newer alphanumeric system in both states in 2013, this was replaced with route B52. In 2006 construction commenced on
Headquarters Joint Operations Command in the
Kowen district of the ACT between
Bungendore and
Queanbeyan. The facility opened in December 2008, and sections of the highway between the
HQJOC turnoff and Queanbeyan have progressively been upgraded to cater for the increased traffic. == Road usage ==