This image shows part of a walking trail and the split-rail fence used to demarcate it to prevent hikers from damaging the root systems of the redwood trees.
The description states:
104 – CALIFORNIA REDWOODS
The redwoods, Sequoia Sempervirens, grow only along the Coast Range from Southern Oregon to Big Sur. The oldest of all living things, they often reach to a height of more than 300 feet and a diameter of 20 feet. For mile after mile the highway curves through the grace and beauty of magnificent groves of these monarchs of the forest.
–The trees have very shallow and wide root systems, which makes them particularly vulnerable to damage from large numbers of hikers or active vehicular traffic.
This image likely dates from the 1950s.