"TinEye is a reverse image search engine. You can submit an image to TinEye to find out where it came from, how it is being used, if modified versions of the image exist, or to find higher resolution versions." You can also enter the URL for an image.
"The holdings of the National Archives Still Picture Branch include 226 photographs taken for this project, most of them signed and captioned by Adams. They were taken at the Grand Canyon, Grand Teton, Kings Canyon, Mesa Verde, Rocky Mountain, Yellowstone, Yosemite, Carlsbad Caverns, Glacier, and Zion National Parks; Death Valley, Saguaro, and Canyon de Chelly National Monuments. Other pictures were taken at the Boulder Dam; Acoma Pueblo, NM; San Idelfonso, NM; Taos Pueblo, NM; Tuba City, AZ; Walpi, AZ; and Owens Valley, CA. Many of the latter locations show Navajo and Pueblo Indians, their homes and activities." From the U.S. National Park Service (NPS). Note: Please scroll down their page for links to the photos.
Photo essays on topics such as: History (Civil Rights, Crime, to World War II), Culture (Animals to Work), Icons (Actors, Actresses, Athletes, Musicians), Curiosities, Photographers (arranged alphabetically by first names).
"This ever-expanding gallery is your entry point into the vast visual holdings of the Archives. The Online Gallery provides free and open research access to over 800,000 items digitized from the Municipal Archives' collections, including photographs, maps, motion-pictures and audio recordings. The holdings are arranged by collection; or you may search All Collections by keyword or any of the advanced search criteria."
"Provides free and open access to over 800,000 images digitized from the The New York Public Library's vast collections, including illuminated manuscripts, historical maps, vintage posters, rare prints, photographs and more." From the New York Public Library.
"Included are images from current exhibits, Smithsonian events and historic collections." Images can be downloaded for personal and educational use and also prints can be purchased. From the Smithsonian Institute.
A compilation of 100 photographs with texts of the American Civil War made by Alexander Gardner and other photographers. "The photographs depict the sites and aftermath of important battles, such as Bull Run, Antietam, and Gettysburg, as well as the forts, military structures, and scenes associated with the war."
"The Getty makes available, without charge, all available digital images to which the Getty holds the rights or that are in the public domain to be used for any purpose." For more information, please see their press release.
"IMAGE provides access to CSU collections of images for teaching and research. The collection includes images for the art history survey and historical images from a wide variety of fields, including political and cultural history, anthropology, biology, medicine and technology. Plans are to add image collections which concentrate on specific subject areas. Access to the collection is currently available through the WorldImages Database which contains more than 50,000 images from throughout the world." From California State University.
"For those who seek knowledge and inspiration from visual materials, the Picture Collection Online presents more than 30,000 digitized images from books, magazines and newspapers as well as original photographs, prints and postcards, mostly created before 1923." Provided by the New York Public Library.