The National Library's photograph album
The album held at the National Library of Wales is thought to be the largest collection and also the only bound album of Watkins' photographs in the United Kingdom. The only other examples of his work in public archives in the United Kingdom are held in the Royal Geographical Society. These are unbound mammoth prints, mostly featuring views of Yosemite National Park and San Francisco.
The bulk of the photographs in the Library's collection are thought to have been taken between 1873 and 1883, dates arrived at by matching as accurately as possible the locations in the album to the dates Watkins is believed to have travelled to certain areas (Palmquist, pp. 199-202). It is difficult to trace the movements of Watkins as he kept few records and most of his photographs are undated. However, it is possible to some extent to date some of his journeys by using evidence in letters to his wife, Frankie, the biography written by his assistant Charles B. Turrill, and other correspondence with his friends and business associates, such as Collis Potter Huntington (who was involved with railways) and J. D. Whitney (who was a member of the California State Geological Survey).