Sign Hill Park Poplar Ave & Rocca Ave, South San Francisco, CA94080 Sign Hill Park, with its entrance at Poplar Avenue at Rocca Avenue, serves as a monument to north San Mateo County.…More In 1996, it was placed on the National Register of Historic Places. This park is the historic site of the giant 60' by 10' hillside letters reading "South San Francisco The Industrial City." Here at the park's entrance you will find openings to Suebert Trail, named after Alphonse Suebert who planted around 5,000 trees in Sign Hill Park, Iris Hill Trail and Letters Trail, all of which span between 0.2 and 0.36 miles. Within the park are also trails called Eucalyptus Loop and Ridge Trail, the longest, which runs for .77 miles. Sign Hill Park is a wonderful place to hike, giving visitors a breathtaking view of south San Francisco.