How did Lincoln establish the concept of democracy and the unity of America?

Lincoln played a great role in keeping the Nation unified. He strongly advocated the integrity of the USA and refused to give the southern states the right to secede from the union. During his inaugural address, he declared that no state had the right to secede after joining the Union. He also gave the famous principle of democracy, i.e., the government of the people, by the people and for the people.