Fairly early on in our history, the United States Supreme Court had occasion (for the first time, but most defintely not the last) to interpret what that phrase meant. In Gibbons v. Ogden (1824), the Court had to determine whether Congress or New York State had authority to grant exclusive licenses to operate steam boats on The Hudson River (separating New York and New Jersey, and then, a major commercial artery). The Court held that since steam boat traffic on the Hudson River involved interstate commerce, it was Congress, and not New York, that had authority to regulate commercial traffic on the river? Thus began a fairly broad interpretation of the phrase "interstate commerce" by the Supreme Court.
Does this decision make sense? What changed during the 1800s that resulted in a complete turn-around by the Court by the end of the century?