Gibbons v. Ogden was mainly about the power of Congress to

The New York Legislature had passed a law giving a monopoly on steamship travel in New York state to a group of investors, including Robert Fulton, the inventor of the steamship Clermont. Among the people who had permission to do business under this monopoly was Aaron Ogden.

Thomas Gibbons, another steamship trader, wanted to use the New York waterways for his business, too. He had been given federal permission to do so. He was denied access to these waterways by the State of New York, which cited its law as enforcement. Gibbons sued Ogden, and the Supreme Court agreed to decide the case.

The majority opinion, written by Marshall, said that the U. S. Constitution had a commerce clause that allowed the federal government to regulate commerce, in this case trade, wherever it might be, including within the borders of a state. Previously, it was thought that the federal government had power over only interstate commerce. But Marshall's opinion said that the commerce clause applied here, too. Thus, the Supreme Court extended the definition of interstate commerce and cemented the power of the federal government over the states when laws conflicted.