He began as a portrait photographer in Seattle, creating images of waterfront Indians. Following the photographic technique called "photogravure", his images were intended to promote photography as legitimate art. His methods were questioned by some, believing he perpetuated untruths and myths about the plight of the American Indian in the early 20th century.
In 1930, worn out and out of money, his work ended. However, he did complete 40,000 images from over 80 tribes.
His original goal was to sell 300 sets of his 20-volume work, but actually sold only 220. They were expensive, leather-bound, books produced for the serious collector. The photogravure process was a painstaking endeavor and expensive, but produced the highest quality of photograph that could be easily reproduced. Photogravure practitioners such as Peter Henry Emerson and others brought the art to a very high standard of expression in the late 19th century. This continued with the work of Alfred Stieglitz in the early 20th century.
Today, the photogravure process is flourishing in the hands of a few artisans practicing the art in dozens of studios around the world.
Here is a short list of links about Curtis and his work:
American Masters Documentary Resource Page
Northwestern University's Digital Library Collection
"The North American Indian" Photographic Images
Some samples of his work: