ed in
Gibbons _v._ Ogden, that when Congress acts upon a particular phase of
interstate commerce, it designs to appropriate the entire field with the
result that no room is left for supplementary State action; _second_,
those in which, in the absence of conflict between specific provisions
of the State and Congressional measures involved, the opposite result is
reached; _third_, those in which the State legislation involved is found
to conflict with certain acts of Congress, and in which the principle of
national supremacy is invoked by the Court. Most of the earlier cases
stemming from State legislation affecting interstate railway
transportation fall in the first class; while illustrations of the
second category usually comprise legislation intended to promote the
public health and fair dealing. More recent cases are more difficult to
classify, especially as between the first and third categories.

THE HEPBURN ACT

No act ever passed by Congress was more destructive of legislation on
the State statute books than the Hepburn Act of 1906,[977] amending the
Interstate Commerce Act. Thus a State statute which, while prohibiting a
railway from giving free passes or free transportation, authorized the
issuance of transportation in payment for printing and advertising, was
found to conflict with the unqualified prohibition by Congress of free
interstate transportation.[978] Likewise, a State statute which
penalized a carrier for refusing to receive freight for transportation
whenever tendered at a regular station was found to conflict with the
Congressional provision that no carrier "shall engage or participate in
the transportation of passengers or property, as defined in this act,
unless the rates, fares, and charges upon which the same are transported
by said carrier have been filed and published in accordance with the
provisions of this act."[979] In enacting this provision, the Court
found, Congress had intended to occupy the entire field. In a third
case, it was held that the Hepburn Act had put it outside the power of a
State to regulate the delivery of cars for interstate shipments;[980]
and on the same ground, a State statute authorizing recovery of a
penalty for delay in giving notice of the arrival of freight was
disallowed;[981] as was also the similar rule of a State railroad
commission with respect to failure to deliver freight at depots and
warehouses within a stated time limit.[982] And in Adams Express Co