Prohibition took hold in 1920 with the Volstead Act and had an impact in the Valley, shutting down vineyards in the Roscoe area (now Sun Valley) and promoting the bootlegging of illicit liquor.

A large still for making applejack was busted in Lankershim in 1921, and another major still was discovered later in a peach orchard along Sherman Way near Woodley Avenue. In 1927 alone, police in the Valley raided twenty makeshift distilleries, arrested 157 bootleggers and seized 50,000 gallons of illegal hooch.

One secret drinking spot that was apparently never busted was in a cave on Chalk Hill, where Ventura Boulevard wound through some magnesium-rich ridges headed west toward Girard (now Woodland Hills). The cave was the haven of Rudolph Langraf, an Austrian who ran a rest stop and gas station called Rudy's Place. He dug the cave originally as a place to keep his eggs and milk cool.

Langraf and his wife mined magnesium chalk from the hills and also took advantage of the weekend tourist traffic that was motoring into the Valley in the 20s and 30s. They mounted binoculars and telescopes at the top of the Topanga Canyon grade and charged ten cents for a view over the Valley's orchards and bean fields.