Togo's harness is completely different from the way it was in real life. In real life, the harness was the same shape as modern skijoring/biking harnesses and had no strap connecting the chest strap to the belly strap. In the film, the harness is similar to a modern X-back harness, but is made of leather with a thick collar.
This story is set in 1925. Sappala tells his wife that his father didn't believe him when he said he was moving to Alaska. Then when the father realized he was, he asked,"Why do you want to move to the United States?" Alaska wasn't made a state until 1959.
American flags when they win their first race. Alaska didn't become a state until 1959 and that scene took place in roughly 1915.
Even though this takes place in January, in Alaska, as usual, you can't see people's breath.
In the film, Togo and Balto both have blue eyes, and so do many other huskies in the film. Some huskies also have heterochromia. The real Togo had brown eyes, as did the real Balto, and the Siberian Husky didn't develop its blue eyes until around the 1940s.
When they take Togo away in the cage, a Phillips head screw can be seen fastening the door. However, the Phillips head screw did not come into use until the 1930's.