Below the solid red line are the 11 states of the Confederacy:
Above the solid Red line, in light blue and gray, are the four Border States with legal slavery, which stayed in the union:
The states in dark blue comprise the rest of Union. Note that in 1863 a large section of Western Virginia, which was largely loyal to the Union, broke away from the Confederacy and form its own state, West Virginia (marked by the dotted red line).
The shaded gray areas illustrate how the Confederacy lost control of its territory over the four years of war.
In 1861, when the war began, there was significant confederate control over the four Border States, though the state governments remained loyal to the union. By the end of 1862, the Union Army had assert control over most of Kentucky and Southern Missouri. In addition, victories at Fort Donelson and Shiloh had put much of Tennessee in Union hands. New Orleans and several other port cities had been taken by Union Naval forces, and a sizable army under Gen. Ambrose Burnside had taken Coastal North Carolina
In December of 1863, despite Gen. Robert E. Lee’s defeat at Gettysburg, the Confederate Army still controlled most of Virginia. But, Gen. Ulysses S. Grant’s victory at Vicksburg gave Union control over the Mississippi River, and most of Eastern and Northern Mississippi, and nearly all of Tennessee.
In 1864, Gen. William T. Sherman’s March to the Sea cut a wide swath through Georgia. Meanwhile, Grant, now commanding the Union Army in the East, backed Lee forces up to Richmond and Petersburg. In Virginia’s Shenandoah Valley, Gen. Philip Sheridan had established Union control.
In 1865, the Union completed its complete victory over Southern forces.