Final answer:
Ulysses S. Grant was the Northern Commander at the end of the Civil War, overseeing the surrender of Robert E. Lee at Appomattox Courthouse on April 9, 1865. This event marked the beginning of the end for the Confederacy, with subsequent surrenders following the 'Appomattox Spirit'.
Step-by-step explanation:
The Northern Commander at the end of the Civil War when the South surrendered was Ulysses S. Grant. After a series of strategic victories and capturing key Confederate cities and industrial centers, Grant pushed Robert E. Lee's depleted army towards a final stand. On April 9, 1865, at the McLean House in Appomattox Courthouse, Virginia, Lee surrendered his Army of Northern Virginia to Grant, signaling the effective end of the Civil War.
Although other Confederate forces still remained in the field, they followed suit in what became known as the "Appomattox Spirit." Significant Confederate resistance ended with General Joseph E. Johnston's surrender on April 26, 1865. The last Confederate general, Stand Watie, surrendered in June 1865, and Confederate President Jefferson Davis was captured on May 10 of the same year.
Grant had previously contacted Lee to suggest that further resistance would be futile. This prompted a series of exchanges between the two, culminating in the historic surrender. Notably, in his farewell address, Lee mentioned the unsparing courage and fortitude shown by his men but acknowledged their defeat by the overwhelming numbers and resources of the Union forces.