The origin of the highway could be traced back to 1945, when the
US Army Corps of Engineers built a “dusty, twisting, narrow” road between
Mount Batulao and
Lemery as the shorter route relative to Route 17, which connected
Imus and
Batangas via Palico in
Tuy and includes the present-day
Aguinaldo Highway,
Tagaytay–Nasugbu Road and Palico–Balayan–Batangas Road. According to Major
Edward M. Flanagan Jr. in his 1948 book, this road was called the Shorty Ridge Road, which likely refers the present-day Diokno Highway. A portion of the highway was affected by a landslide caused by
Typhoon Melor (Nona) in December 2015; fortunately, the entire stretch was open to traffic as of December 17. In August 2016, a section of the highway in
Calaca was closed to traffic due to road slip and collapsed slope protection following the continuous heavy rains in the area. As a result, the Diokno Bridge was reconstructed beginning in the first quarter of 2017. The reconstructed bridge was inaugurated on November 13, 2018. == References ==