This is the famous trestle across the Battle River. It's one of the longest and highest in the country. 2775 feet long and 195 feet high. Built in 1907-08. It's on the CN Rail main line.
Looks so much like the High Level Bridge, viaduct, in Lethbridge, that I had to check! I guess the Lethbridge one, appearing of similar design, has the distinction of being the largest! I used to live in Lethbridge but did no photography at the time. Some day a return to Alberta is warranted for some serious image making!
Eb