USGS Denver Library Photographic CollectionThis websites holds more than 500,000 still photographs, slides, glass plate slides, lantern slides, negatives, and sketches starting in the 1870's. USGS scientists took this images as part of their field studies. Subjects include earthquakes, volcanoes, geologic formations, minerals, historical mining operations, national parks, USGS portraits, and other photographs of historic and earth science events. You can freely download selected images from the collection.