The gospel hymn that Hester Sue sings at the end of this episode, "Stand By Me," was not written until 1905 by Charles Albert Tindley. The period of this episode is the late 1880's.
When Nels is bringing medicine into the Blind School, people are bringing out what looks like a dead body. But right before they go off screen, the second man drops one side of the stretcher, and nothing falls off.
Doc Baker sends a telegram to the hospital in Rochester. The train from Rochester is held up due to a blizzard. When Charles and Johnathan get the medicine, the crates indicate that they are from Rochester New York. It should have been Rochester Minnesota.