South San Francisco Hillside Sign, Historic hillside sign in South San Francisco, United States.

The South San Francisco Hillside Sign is a large white concrete sign mounted on a hillside overlooking the city. The letters are visible from great distances and prominently shape the city's appearance.

The sign was initiated in 1923 by the Chamber of Commerce and later replaced with larger concrete letters in 1929 to promote industrial growth. This expansion reflected the city's early economic ambitions and development.

The sign was proposed by the South San Francisco Chamber of Commerce as "civic boosterism", advertising the city's welcome to industry; its placement made it readable from El Camino Real, the Bayshore Highway, the train and Mills Field. In the 1980s a movement sought to change the wording to "the industrious city"; the Historic Preservation Commission and Historical Society pushed back, winning National Register listing in 1996. In June 2026 volunteers painted the words red, white and blue for the 250th anniversary of the United States, in the order red, blue, white so the nickname stayed brightest.

Sign Hill Park offers hiking trails that lead up to the letters and allow close-up views of the sign. Best access is through parking areas at the base of the hill.

The letters use a special optical technique that makes them appear the same size from different distances and angles. This creates a uniform look despite the letters having different actual heights.