It was 150 years ago today that Robert E. Lee surrendered to General Ulysses S. Grant at Appomattox, effectively ending the confederate states' rebellion against the United States. For all practical purposes, the American Civil War was over; and April 9, 1865, was thus a great day in American history, not just for ending four years of intense conflict and human suffering, but for what was accomplished on the battlefield that politics could not accomplish..
Most wars are fought (at least ostensibly) to solve certain specific problems. Some fail - for example, the War of 1812, which accomplished next to nothing at all, and World War I, which left the world in almost every respect worse off that when it started. Some succeed - for example, the American Revolution, which solved the 13 colonies' problem (as they perceived it) of being part of the British Empire, and World War II, which solved the problem of German aggression and Japanese imperialism. For its part, the American victory in the Civil War solved the problem of the U.S. Constitution's greatest failing - slavery. Slavery has often been called "the original sin of American society." It was a problem that the political process clearly could not resolve and which was finally only resolved on the battlefield. The 13th, 14th, and 15th Amendments to the Constitution then wrote into law what had been made possible by a decisive military victory - in the process overturning the US Supreme Court's infamous Dred Scott decision, the most ignominious and morally repugnant Supreme Court decision of the 19th century (much as Roe v. Wade would later be the most ignominious and morally repugnant decision of the 20th century.)
The Civil War also solved the problem of federalism. It didn't do so completely, of course, for we are still a union of states, but it solved it to the extent that it settled where ultimate sovereignty really lies - in the Federal Government and only in the Federal Government. Pre-Civil War politics had been burdened by theories of secession and nullification and states' rights, all of which were completely discredited by their proponents' defeat on the field of battle.
Or so it seemed. Sadly, the U.S. remains still sectionally divided and profoundly polarized ideologically - and in ways which seem viscerally reminiscent of the divisions which that Civil War was supposed to have already resolved 150 years ago. So today is a good day to recall what that Civil War was about, what the stakes were for this country and its people then and what they still are now, in light of the ways in which our society has recently regressed.
Grant did defeat Lee. Lincoln's superior moral vision triumphed over slavery and secession. The challenge today is to remember what that means and to return to building a more just and equal society upon the new and improved foundation of the post-civil War American Constitution.