I love old photos and am thrilled that many organizations (such as libraries) have put historical images online.
Here's a link for historical Colorado photos.
http://photoswest.org
My favorite way to surf this site is to click the "search" button then enter a keyword and just see what comes up. If you're looking for something specific, be sure to try variations on a word (bike, bicycle, cycling, etc.) because the site has a ton of great stuff but it's not necessarily cataloged uniformly.
If you know of other sites, please add to the list.![]()