Samuel Nelson, Pennsylvania v. Wheeling and Belmont Bridge Company…
“ We do not enter upon the question, whether or not congress possess the power, under the authority in the constitution, 'to establish post-offices and post-roads,' to legalize this bridge; for, conceding that no such powers can be derived from this clause, it must be admitted that it is, at least, necessarily included in the power conferred to regulate commerce among the several States. The regulation of commerce includes intercourse and navigation, and, of course, the power to determine what shall or shall not be deemed in judgment of law an obstruction to navigation ”
