In 1978, the Barrenjoey Road area came to national attention due to the unsolved disappearance of Trudie Adams.

164 was declared along this road on 8 August 1928, from Newport to Mona Vale (and continuing south via Narrabeen, Dee Why, Balgowlah, along Military Road and Falcon Street through Mosman, then along Miller Street to the intersection with Great Northern Highway (today Pacific Highway) and Mount Street in North Sydney);[2] with the passing of the Main Roads (Amendment) Act of 1929[4] to provide for additional declarations of State Highways and Trunk Roads, this was amended to Main Road 164 on 8 April 1929.

Trudie Adams disappeared in the early hours of 25 June 1978 after attending a dance at the Newport Surf Life Saving Club.

Her disappearance is significant in that it sparked New South Wales' biggest missing person search at the time,[11] sparked extensive and ongoing national media attention, and eventually a A$250,000 reward.

[12][13] Barrenjoey Road is entirely contained within the Northern Beaches Council local government area.