ning previous holdings
which had laid down the doctrine that to be subject to Congress's power
to regulate commerce a stream must be "navigable in fact," said: "A
waterway, otherwise suitable for navigation, is not barred from that
classification merely because artificial aids must make the highway
suitable for use before commercial navigation may be undertaken,"
provided there must be a "balance between cost and need at a time when
the improvement would be useful. * * * Nor is it necessary that the
improvements should be actually completed or even authorized. The power
of Congress over commerce is not to be hampered because of the necessity
for reasonable improvements to make an interstate waterway available for
traffic. * * * Nor is it necessary for navigability that the use should
be continuous. * * * Even absence of use over long periods of years,
because of changed conditions, * * * does not affect the navigability of
rivers in the constitutional sense."[365]

Purposes for Which Power May be Exercised

Furthermore, the Court defined the purposes for which Congress may
regulate navigation in the broadest terms, as follows: "It cannot
properly be said that the constitutional power of the United States
over its waters is limited to control for navigation. * * * That
authority is as broad as the needs of commerce. * * * Flood protection,
watershed development, recovery of the cost of improvements through
utilization of power are likewise parts of commerce control."[366] These
views the Court has since reiterated.[367] Nor is it by virtue of
Congress's power over navigation alone that the National Government may
develop super-power. Its war powers and power of expenditure in
furtherance of the common defense and the general welfare supplement its
powers over commerce in this respect.[368]

Congressional Regulation of Land Transportation

EARLY ACTS; FEDERAL PROVISION FOR HIGHWAYS

The acquisition and settlement of California stimulated Congress some
years before the Civil War to authorize surveys of possible routes for
railway lines to the Pacific; but it was not until 1862, in the midst of
war, with its menace of a general dissolution of the Union, that more
decisive action was taken. That year Congress voted aid in the
construction of a line from Missouri River to the Pacific; and four
years later it chartered the Union Pacific Company.[369] First and last,
litigation growing out of this type of legislation