The topic of discussion for this Constitution Monday comes from Article I.8.3: "The Congress shall have Power To regulate Commerce … among the several States." This provision in the U.S. Constitution gives the right and responsibility to Congress to "create a common market of free trade between all of the states and regulate interstate commerce of all kinds." This clause is the one used by the Obama Administration to justify forcing Obamacare on our nation.
Before the Constitution was written, the various states were regulating commerce with their neighbors in such a way that they were gouging each other in an effort to promote prosperity in their state. Even though the emphasis was at first on "commerce," it soon moved to "regulate." The first court cases were about attempts by states to gain special advantage by interfering with commerce across state borders. Now there are so many government regulations on interstate commerce that it is hampering the economic growth of our nation.
The U.S. Supreme Court interpreted the word "commerce" to cover "every species of movement of persons or things" - including all kinds of communications, all kinds of intelligence transmission, all kinds of commercial negotiation or anything else that may sooner or later be transported across state lines.
The emphasis has now changed to "regulate." "According to Supreme Court rulings, the government is empowered to adopt measures which will protect, foster, control, constrain, or prohibit commerce for the welfare of the public so long as the `due process' clause of the Fifth Amendment is not violated.
"Streambeds belong to the respective states, but the navigable waters are exclusively under federal control. The government has powers as broad as the needs of commerce may warrant. It includes flood protection and watershed development; and it has even been held that the government can use the water to develop power and sell it to help recover the costs of improvements. If a waterway is not naturally navigable until dams are built and improvements made, the federal government can erect a dam and thereafter has authority to regulate the dam, reservoir, and resulting waterway as though it had always been navigable.
"The government has the power to establish and regulate interstate highway systems. It need not build these highways directly but may charter private corporations to do it, and these corporations can be vested with the power of eminent domain to secure the necessary land for the building of such highways. The government may also exempt these federal franchises from state taxation (since otherwise the states could use taxes to destroy or inhibit these projects)."
Ideas and quotes are from W. Cleon Skousen in The Making of America: The Substance and Meaning of the Constitution, pp. 400-401. This book has approximately ten pages covering this topic so there is much more information available in an easily understood style.