Today marks the de Young's debut of "Portals Of The Past," the exhibition of photographer Willard E. Worden's photographs of San Francisco just after the turn of the 20th century.

The exhibition, which will run until February 2016, is named for Worden's photograph of the remains of a Nob Hill estate destroyed in the 1906 earthquake and relocated to Golden Gate Park in 1909, and chronicles San Francisco's coast and Golden Gate Park at and around the time of the Panama-Pacific International Exhibition.

2015 is, of course, the 100th anniversary of the 1915 exhibition, which gave us such architectural lights as the Palace of Fine Arts, the Legion of Honor, and Bill Graham Auditorium.

Willard Worden was one of the exhibition's official photographers, so a lot of the photographs on display beginning today tie into the de Young's upcoming fall show about the Panama-Pacific Exhibition, "Jewel City."

Worden's photography is available, in part, by way of the San Francisco Public Library's collection. The library has also made available an extensive catalog of ephemera from and related to the Pan-Pacific Expo, including a map of the fairgrounds and a huge digital catalog of photographs from it, which you can peruse at your leisure here.