Pfost[546] the generation of electricity in a State
was held to be distinguishable from its transmission over wires to
consumers in another State, and hence taxable by the former State.
Likewise, a State statute imposing a privilege tax on the production of
mechanical power for sale or use did not contravene the interstate
commerce clause although applied to an engine operating a compressor to
increase the pressure of natural gas and thereby permit it to be
transported to purchasers in other States.[547] Similarly, a tax so much
per pound on shrimp taken within the three-mile belt of the coast of the
taxing State was valid, since the taxable event, the taking of the
shrimp, occurred before they could be said to have entered the
interstate commerce stream.[548]

PRODUCTION FOR AN ESTABLISHED MARKET

But while the production of goods intended for the interstate market is
taxable by the State where it takes place, their purchase for an
established market in another State is interstate commerce and as such
is neither regulatable nor taxable by the State of origin, provided at
any rate their trans-shipment is not unduly delayed.[549] Thus, oil
gathered into the pipe lines of a distributing company and intended for
the most part for customers outside the State, is in interstate commerce
from the moment it leaves the wells;[550] and a like result has been
reached as to natural gas.[551] "The typical and actual course of
events," says the Court, "marks the carriage of the greater part as
commerce among the States and theoretical possibilities may be left out
of account."[552]

REJECTION OF THE ORIGINAL PACKAGE CONCEPT IN INTERSTATE COMMERCE

But the question also arises as to when goods entering a State from
another State become part of the mass of property of the former and
hence taxable by it? In Brown _v._ Maryland,[553] Chief Justice
Marshall, had remarked at the close of his opinion, "We suppose the
principles laid down in this case, apply equally to importations from a
sister State."[554] Forty-two years later, in Woodruff _v._ Parham,[555]
an effort was made to induce the Court, in reliance on this dictum, to
apply the original package doctrine against a Mobile, Alabama tax on
sales at auction, so far as it reached "imports" from sister States.
The Court refused the invitation; first on the ground that Marshall's
statement was _obiter_, the point not having been involved in Brown _v._
Maryland; second, because u