James Madison to Joseph C. Cabell, 13 Feb. 1829
For a like reason, I made no reference to the "power to regulate commerce among the several States." I always foresaw that difficulties might be started in relation to that power which could not be fully explained without recurring to views of it, which, however just, might give birth to specious though unsound objections. Being in the same terms with the power over foreign commerce, the same extent, if taken literally, would belong to it.
Yet it is very certain that it grew out of the abuse of the power by the importing States in taxing the non-importing, and was intended as a negative and preventive provision against injustice among the States themselves, rather than as a power to be used for the positive purposes of the General Government, in which alone, however, the remedial power could be lodged.
http://press-pubs.uchicago.edu/founders/documents/a1_8_3_commerces19.html
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Excerpt from Chief Justice John Marshall's opinion in Gibbons:
They [inspection laws] form a portion of that immense mass of legislation, which embraces everything within the territory of a State, not surrendered to the general government: all which can be most advantageously exercised by the States themselves. Inspection laws, quarantine laws, health laws of every description, as well as laws for regulating the internal commerce of a State, and those which respect turnpike roads, ferries, &c., are component parts of this mass.
No direct general power over these objects is granted to Congress; and, consequently, they remain subject to State legislation.
-J. Marshall, Gibbons v Ogden, 1824
Since the New Deal, Congress HAS taken direct general power over many of these objects. Not only has the original meaning been violated, so has stare decicis.
There were issues about banking and stock issuance among the states, about systems of commerce. I think that early on, the “among” the several states was meant to homogenize those systems, not to regulate commerce itself.