The etymology of the word, "cum merce (with merchandise)" carries the primary meaning of traffic--i.e., "to buy and sell goods; to trade" (Webster's International). This narrow conception was replaced in the great leading case of Gibbons _v._ Ogden, 9 Wheat. 1 (1824), by a much broader one, on which interpretation of the clause has been patterned ever since. The case arose out of a series of acts of the legislature of New York, passed between the years 1798 and 1811, which conferred upon Livingston and Fulton the exclusive right to navigate the waters of that State with steam-propelled vessels. Gibbons challenged the monopoly by sending from Elizabethtown, New Jersey, into the Hudson in the State of New York two steam vessels which had been licensed and enrolled to engage in the coasting trade under an act passed by Congress in 1793. Counsel for Ogden (an assignee of Livingston and Fulton) argued that since Gibbons' vessels carried only passengers between New Jersey and New York, they were not engaged in traffic and hence not in "commerce" in the sense of the Constitution. This argument Chief Justice Marshall answered as follows: "The subject to be regulated is commerce; * * * The counsel for the appellee would limit it to traffic, to buying and selling, or the interchange of commodities, and do not admit that it comprehends navigation. This would restrict a general term, applicable to many objects, to one of its significations. Commerce, undoubtedly, is traffic, but it is something more--it is intercourse."[308] The term, therefore, included navigation--a conclusion which Marshall supported by appeal to general understanding, to the prohibition in article I, § 9, against any preference being given "'* * * by any regulation of commerce or revenue, to the ports of one State over those of another,'" and to the admitted and demonstrated power of Congress to impose embargoes.[309]
Later in his opinion Marshall qualified the word "intercourse" with the word "commercial."[310] Today "commerce" in the sense of the Constitution, and hence "interstate commerce" when it is carried on across State lines, covers every species of movement of persons and things, whether for profit or not;[311] every species of communication, every species of transmission of intelligence, whether for commercial purposes or otherwise;[312] every species of commercial negotiation which, as shown "by the established course of the business," will involve sooner or later an act of transportation of persons or things, or the flow of services or power across State lines.[313]