There's no single moment that historians universally agree marked the decisive shift in the American Civil War. That said, many people look to two events in early July of 1863 as the war's turning point: the Battle of Gettysburg and the fall of Vicksburg after a prolonged siege.
At Gettysburg, Confederate General Robert E. Lee saw his ambitious push northward come to a halt. Over in Vicksburg, the successful conclusion of the siege fulfilled the objectives of the Anaconda Plan — a strategy built around blockading Confederate ports and driving Union forces down the Mississippi River to split the Confederacy into two isolated halves.
Even so, the Union's growing dominance on the battlefield didn't bring swift resolution. Brutal combat dragged on, and it wasn't until 1865 that a Ceasefire Agreement of the Confederacy finally materialized.
In the popular imagination, the war's end is most closely tied to one iconic moment: Confederate General Robert E Lee handing his surrender to Union General Ulysses S. Grant on April 9 in Appomattox County.
After retreating from the Confederate capital of Richmond, VA, Lee had been making his way toward North Carolina when General Philip Sheridan cut off his path. Believing he faced nothing more than a screen of light cavalry, Lee launched a final effort to punch through the Union lines.
What Lee discovered, though, was that Sheridan's cavalry had the support of two full infantry corps — leaving surrender as his only remaining option. This act set off a cascade of surrenders across the South, effectively closing the book on four grueling years of warfare.
Yet several significant developments still had to unfold before U.S. President Andrew Johnson would officially proclaim the American Civil War at an end on August 20 of 1866.
Consider the circumstances that brought Johnson to the presidency in the first place: his predecessor, U.S. President Abraham Lincoln, had been assassinated on April 14. Then, on May 5, Confederate President Jefferson Davis convened his Cabinet for a final session, an event that formally dissolved the Confederate government. Just five days later, on May 10, Union forces captured Davis himself, tying up yet another loose end.
By the time Johnson issued his formal declaration, there was absolutely no question — not even the faintest shadow of doubt — that the Union had emerged as the victor of the American Civil War.