The kitschy white letters declaring “South San Francisco The Industrial City” are celebrating their 100th birthday today, and it turns out you can hike right up to those letters and wish them a happy birthday.

Travelers who arrive at San Francisco International Airport and then head to the city, or everyday commuters heading northbound on Highway 101, are well familiar with the giant hillside white letters that announce “South San Francisco The Industrial City.”  It turns out they have been there longer than SFO has existed — the airport opened in 1927, whereas the South San Francisco sign-letters were originally put up in 1923. And as Bay Area News Group points out, the South San Francisco sign turns 100 years old today, November 22.

The News Group’s article notes that South San Francisco’s Parks and Recreation Department just repainted those white letters, and you can hike right up to them and see them up close on something called the Sign Letters Trail. An SFGate article from 2021 is full of pictures showing how close you can get to the letters.

Much like the famed Hollywood letter sign (which also turned 100 years old this year), the sign was an example of an early 20th-century trend known as “civic boosterism.” Redwood City’s similar “Climate Best by Government Test” sign went up two years later. These slogans obviously sound quite dated, but the signs have stood the test of time and remained beloved.

While the letters all appear uniform from a distance, that’s an optical illusion, and they’re not all the same size. You get a sense of this from the above video, taken when there was a brush fire on the hill in 2020. They are spaced and arranged to appear even and consistent on the contoured hillside. According to the sign's National Register of Historic Places nomination, the letters range from 48 to 65 feet in  height.

You may be familiar with some graffiti pranks that have been played with the letters in years past: UC Berkeley students painted the C, A, and L yellow as a pro-Cal prank to tease Stanford on the week of their Big Game, Giants fans painted an S and an F orange after winning the World Series, and who can forget back in 2019 when some joker altered the sign to read “The Industrial Tity.”

And it seems it was a pastime in years of old that kids would slide down the letters on cardboard boxes. This is no longer allowed. “I get the appeal of sliding,” City of South San Francisco natural resources specialist Candace LaCroix tells the News Group. “But we’re trying to preserve a historic landmark that is prone to erosion issues.”

And there’s more to preserve up on Sign Hill than just the signs. According to a volunteer group called the Sign Hill Stewards, the area “provides critical habitat for wildlife on the San Francisco Peninsula,” and “is home to a diverse set of species, including the endangered Mission blue butterfly.” That group meets on the hill weekly to install native plants and remove invasive species, and you can join them any week to help, including at a session this coming Saturday.

Related: Wildfire Breaks Out On Hillside Next to Famed South San Francisco Sign, Threatening Homes [SFist]

Image: Willis Lam via Wikimedia Commons