Most of the components of the route are old roads. The section of Military Road through
Cremorne and
Mosman was first built in the 1820s. The earliest bridge at
The Spit, linking Mosman to
Manly, opened in 1923, and was then rebuilt in the late 1950s with new, wider, approach roads on the southern (Spit Road) and northern sides (Manly Road) of the bridge. 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 (MRB). Main Road No. 164 was declared along this road on 8 August 1928, from the intersection of Great Northern Highway (today
Pacific Highway) and Mount Street in North Sydney, then along Miller and Falcon Streets and Military Road via Cremorne, Balgowah, Dee Why and Narrabeen to Mona Vale (and continuing northwards to
Newport); to provide for additional declarations of State Highways and Trunk Roads, this was amended to Main Road 164 on 8 April 1929. Main Road 164 was officially named
Pittwater Road, between Mona Vale Road in
Mona Vale and Condamine Street in
North Manly (and continuing northwards to
Church Point, and southwards to Raglan Street in
Manly), on 10 January 1951. The
Burnt Bridge Creek Deviation opened in 1985 to bypass the congested Balgowlah shopping strip, offering 3 kilometres of freeway-standard motoring. The western end of Main Road 164 through North Sydney was re-aligned from Miller Street, to Falcon Street and its intersection with
Pacific Highway in
Crows Nest, on 22 January 1993. The passing of the
Roads Act of 1993 updated road classifications and the way they could be declared within New South Wales. Under this act, the A8 retains its declaration as part of Main Road 164. The route was signed State Route 14 across its entire length (and continuing north along Barrenjoey Road to Palm Beach) in 1974. The whole route was re-designated
Metroad 10 in 1998, between North Sydney and Mona Vale. Traffic headed south-east on
Warringah Freeway originally had no ability to exit the freeway to enter Falcon Street, so the original Metroad 10 route was extended further west via Pacific Highway to meet
Gore Hill Freeway at
Artarmon. When north-facing, tolled off-ramps were constructed directly connecting Warringah Freeway to Falcon Street in 2007, Metroad 10 route was truncated to Falcon Street's interchange with
Warringah Freeway. With the conversion to the newer alphanumeric system in 2013, Metroad 10 was replaced by route A8. ==Major intersections==