What does this line graph tell us about the demographic changes after world war 2

Many Southern states made it clear that if Lincoln was elected, they would secede (leave the Union). The South was against Lincoln because he opposed slavery. South Carolina was the first to secede in December 1860. Six other Southern states followed: Mississippi, Florida, Alabama, Georgia, Louisiana, and Texas. After Lincoln's inauguration, Virginia, Arkansas, Tennessee, and North Carolina also left the Union. These states became known as the Confederacy. The secession of the Southern states led to the first shots of the Civil War when the Confederates seized Fort Sumter in South Carolina in April 1861. 

Lincoln faced the greatest national crisis of any U.S. President. He hated war and the death and destruction it would bring. However, he accepted war as the only means of saving the Union. He warned the South in his Inaugural Address:

"In your hands, my dissatisfied fellow countrymen, and not in mine, is the momentous issue of civil war. The government will not assail you... You have no oath registered in Heaven to destroy the government, while I shall have the most solemn one to preserve, protect and defend it." (Abraham Lincoln Web Site) 

As the nation neared the third year of the bloody Civil War, President Lincoln issued the historic Emancipation Proclamation on January 1, 1863. The proclamation declared "that all persons held as slaves" within the rebellious states "are, and henceforward shall be free." 

This proclamation actually freed few people. It did not apply to slaves in the Border States of Missouri, Kentucky, Maryland, and Delaware; nor did it affect slaves in southern areas already under Union control. Naturally, the states that had seceded did not act on Lincoln's orders. But the proclamation showed Americans — and the world — that the war was being fought to end slavery. 

Although the Emancipation Proclamation did not immediately free a single slave, it changed the way black men were accepted during the war. Black men could join the Union Army and Navy. The liberated could become the liberators. By the end of the war, nearly 200,000 black soldiers and sailors fought for the Union and freedom. 

On November 19, 1863, President Lincoln gave his famous Gettysburg Address in Gettysburg, Pennsylvania. The speech dedicated the battlefield to the soldiers who had died there. The battle site became a military cemetery. Lincoln stated in his moving speech: "...we here highly resolve that these dead shall not have died in vain — that this nation, under God, shall have a new birth of freedom — and that government of the people, by the people, for the people, shall not perish from the earth." (The National Archives.)