Factual error: No airport in NYC has the view of the New York City skyline that Kevin has when he realizes that his family is in Florida and he's in New York.
Factual error: During the big Newsies rally when Medda is singing "High Times", as she is swinging, lighted exit signs can be seen. I don't believe that those were around in 1899.
Factual error: The baby is expanded to approximately fifty times his height, width and girth but it's explicitly stated that he retains his orginal mass. This means he will have the same volume as one hundred and twenty five thousand babies of his original size, but will weigh the same as before he was enlarged! That child is going to weigh much less than the volume of air he displaces. He's going to float away.
Factual error: The Newton children don't age at all between Beethoven coming to live with the family as a puppy and when he becomes an adult dog.