This image shows four engines pulling a tourist train across the high trestle over the Montreal River near Sault Sainte Marie, Canada.
Prismaflex Color – Wilson, Dryden, Ont.
The description states:
The Montreal River trestle, a breathtaking crossing at Mileage 92 north of Sault Ste. Marie, Ontario. – Algoma Central Railway, Agawa Canyon Tour
–Such tours through forested areas are common even today, particularly during the Autumn when the trees change color. Also visible in the background is a dam and hydroelectric plant built on the Montreal River. The four engines in use indicate a very long train of passenger coaches.
This image likely dates from the 1960s, when the tourist service started.