This is a list of online image archives related to the western U.S. and Canada.

From American Memory at the U.S. Library of Congress:

History of the American West.
Photos from a collection at the Denver Public Library (http://www.denver.lib.co.us/).
http://memory.loc.gov/ammem/award97/codhtml/hawphome.html

The American Indians of the Pacific Northwest collection.
http://memory.loc.gov/ammem/collections/pacific/

Prairie Settlement: Nebraska Photographs and Family Letters.
From Nebraska State Historical Society (http://www.nebraskahistory.org).
http://memory.loc.gov/ammem/award98/nbhihtml/pshome.html

Braceros in Oregon Photo Collections
Oregon State University Archives
http://digitalcollections.library.oregonstate.edu/cdm4/client/bracero/

California Heritage Collection at the Online Archive of California
http://sunsite.berkeley.edu/CalHeritage/

Las Vegas and Water in the West
From the UNLV Libraries Digital Collections and Exhibits
http://www.library.unlv.edu/water/

Oregon Historic Photograph Collection
From the digital collections of the Salem Public Library
http://photos.salemhistory.org/

United States Forest Service Photo and Video Library
http://www.fs.fed.us/photovideo/

British Columbia Archives at the Royal BC Museum
http://www.bcarchives.gov.bc.ca/visual/visual.htm

CN Images of Canada Gallery Collection of photos held by Canadian National.
Photos are from photographers hired by Canadian rail companies, chiefly Canadian National Railways.
http://216.94.16.48/index1.html

Images Canada, a project of the National Library (http://www.collectionscanada.ca/)
http://www.imagescanada.ca/r1-200-e.html

TimeLinks Image Archive for Manitoba
http://timelinks.merlin.mb.ca/photo.htm

Alaska and Western Canada Collection
From the University of Washington Libraries Digital Collections
http://content.lib.washington.edu/alaskawcanadaweb/index.html