Shasta dam under construction, California (LOC) 194-. Part of a set from a Library of Congress collection of public domain photographs taken in color in the early 1940's with cameras using larger formats than 35mm. Titles can be searched on the LOC site or by going to Flikr and searching under the title "Library of Congress." Photographs have been cropped slightly and the color and contrast adjusted to be more favorably displayed.
When you consider the scale involved in this picture it is really very impressive.