The University of Alberta Libraries now has a collection of postcards available from the Peel’s Prairie Provinces web site (the site focuses on the history of western Canada and the Canadian prairies.) The postcards launched the week of December 14 and are available at http://peel.library.ualberta.ca/browse/postcards/.
The over 15,000 postcards here are divided into a dozen categories, including People, Events, Business, Organizations, and Vehicles. Click on a category and you’ll get a pop-up window that allows you to go even further, browsing sub- and sub-sub-categories. (I clicked on Objects and ended up browsing Fire Hydrants.)
Because you can browse so specifically you might not see many postcards on the page you get. My Fire Hydrants result gave me one result, a 1910 postcard of a train station (the hydrant is in the foreground.) Click on the thumbnail of the postcard in the results page and you’ll get a larger image as well as expected details about the card (physical description, notes about the subject of the card) and unexpected (address on the card! Message on the card! This information wasn’t always available but what a surprise when it was!)
Results are presented 48 to a page with thumbnails and brief descriptions, with thumbs leading to a detail page. Images could be a bit bigger but they’re good enough; the scans are high-res and you can download them if you want to enlarge them and look at them more closely.
As long as you’re here, jump up a level and visit Peel’s Prairie Provinces, which contains digitized newspapers (French and English) and business/residence directories, among other offerings. The newspaper holdings in particular are very extensive.