As a practical matter, the Civil War established the supremacy of the federal government over the formerly sovereign states. The states lost any power of resisting the federal government's usurpations, and the long decline toward a totally consolidated central government began.
By 1973, the federal government was so powerful that the U.S. Supreme Court could insult the Constitution by striking down the abortion laws of all 50 states; and there was nothing the states, long since robbed of the right to secede, could do about it. That outrage was made possible by Lincoln's triumphant war against the states, which was really his dark victory over the Constitution he was sworn to preserve.
-Joseph Sobran
http://lewrockwell.com/sobran/sobran-j31.1.html