https://www.siliconvalley.com/2023/11/22/south-san-franciscos-hillside-sign-celebrates-its-100th-birthday/

The Industrial City sign in South San Francisco turns 100 years old today.

The 65-foot-tall cement letters on the southern flank of San Bruno Mountain are one of California’s largest examples of civic boosterism, an early 20th-century tradition of carving town’s initials into hillsides or building lighted roadway entry arches, like Redwood City’s “Climate Best by Government Test” sign.