Trivia: Producers Gale Anne Hurd and Sam Mercer wanted to film the movie at the American Museum of Natural History in New York. However, the museum's administration was afraid that the film would not only cast the museum in an unflattering light, but it would also scare kids away from the museum. They were given permission by the Field Museum of Natural History in Chicago to film there, because they loved the movie's premise.
Trivia: The Kathoga has only five minutes of screen time in the entire film.
Chosen answer: Cost of shipping would be much cheaper. However, the Mississippi River System is connected to the Illinois Waterway, which continues to the Great Lakes Waterway. This means Chicago is connected to the Gulf of Mexico (which is accessible to South America). There would be no need to ever be on the road.