Melissa Brandts wasn't trying to take a photo of this ground squirrel at Banff National Park. She'd set up the camera's timer so that she'd have a nice picture of herself and her husband, with spectacular Lake Minnewanka in the background.
If you liked the Flickr Library of Congress post, here's another to a site that posts hi-res (seemingly public domain) images. Some great images from late 1800s to 1960s.
Images are made by finding old photographs of places, printing them out, and then holding the print up in the modern day location that the original photograph was taken.