For general background, see the Lincoln campaign broadside, "How the War Commenced and How Near It Is Ended," ID # 1069. This map predates the Lincoln broadside by some six months.
"We give on page 181 a dissolving view of the Rebellion, representing the proportions to which it has been diminished since October 1, 1861. The light tint on the map shows the territory which since that time has been conquered by our forces, amounting to at least one half of the original Confederacy. And the half which has been left has, as the reader will perceive, been entirely cut into two separate sections by our possession of the Mississippi and our victories in East Tennessee." (Harper's 187).
The collection includes four maps from 1863 and 1864 illustrating the progress of the war in this manner: ID #2300 (from the New-York Daily Tribune, August 10, 1863) (not yet online); ID #2152 (from The New York Herald, February 10, 1864); ID #1070 (from Harper's Weekly, March 19, 1864); ID #1069 (Republican campaign broadside, October 1, 1864).