so, this is something, I'd been believing that these elevated watchtowers were for police, but instead, I learned they are coigns of vantage for railroad or trolley switchmen

“View of the intersection of Main, Spring, and 9th streets in downtown Los Angeles, circa 1937. A uniformed man sits in a booth on top of a pole in the foreground of this corner as pedestrians walk by underneath.

“Historical Note: In the early part of the 1900s, elevated booths were used by the Los Angeles Railway and the Yellow Cars as a switchman’s tower to control the flow and path of streetcars through the intersection.”

http://route22ny.tumblr.com/post/173305543222/view-of-the-intersection-of-main-spring-and-9th