In 1909, LRN 5, which would become known as California Route 17 in 1936, was built as a main highway between Santa Cruz and San José through the Santa Cruz Mountains. In 1950, when the Lexington Reservoir was created, the towns of Alma and Lexington were submerged under he reservoir and the road was rerouted around the new body of water.
The History Of California Route 17
Hamilton Historical Records 