The markings were a secret communication system used by wanderers in the 1910s and 1920s—and represent an important part of American history.

In 2000, Phillips, an environmental analysis professor at Pitzer College, was searching for traces of old graffiti with a group of friends when they stumbled upon a nearly century-old collection of scribbles. Written on the walls of the bridge were roughly 20 names, accompanied by dates indicating that the markings were made as far back as 1914

Two homeless men walk under a bridge along the Los Angeles River, where almost extinct forms of American hieroglyphics known as hobo graffiti were discovered.
Two homeless men walk under a bridge along the Los Angeles River, where almost extinct forms of American hieroglyphics known as hobo graffiti were discovered. © JAE C. HONG/AP

“It was one of those few times when you’re actually looking for something and you find it,” Phillips tells CityLab. She’s been studying the history of L.A.’s graffiti for an upcoming book. “Being able to look at this wall that was still intact and completely untouched by any contemporary graffiti, it was absolutely remarkable that it survived.” 

She’s been able to document a handful of examples of hobo graffiti from the past century—at least one from every decade beginning in the 1910s. Phillips considers that earliest era to be the “turn-of-the-century for hoboing.”

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Graffiti left by hobos are seen under a bridge in Los Angeles. The writings and drawings, some dating to 1914, were written with utensils such as grease pencils or etched into the concrete under the103-year-old bridge spanning the Los Angeles River.
Graffiti left by hobos are seen under a bridge in Los Angeles. The writings and drawings, some dating to 1914, were written with utensils such as grease pencils or etched into the concrete under the103-year-old bridge spanning the Los Angeles River. © JAE C. HONG/AP