In the northern states, however, there were few slaves. For in these northern states there was not much that slaves could do which could not be done just as well by white men. So it did not pay to keep slaves, and gradually slavery was done away with.
But in the South it was different. There it was so hot that white men could not do the work in the rice and cotton fields. And the planters believed that without Negro slave labour it would be impossible to make their plantations pay.
Then, when the power of steam was discovered and many new cotton spinning machines were invented, the demand for cotton became greater and greater; the Southern planters became more sure than ever that slavery was needful. They also became afraid that the people in the North would want to do away with it, and if the number of the states in which slavery was not allowed increased it would be easy for them to do this. So the Southerners determined that if non-slavery states were admitted to the Union slavery states must be admitted also to keep the balance even.
Now when Maine and Missouri both asked to be admitted as states the Southerners refused to admit Maine as a free state unless Missouri was made a slave state to balance it.
There was tremendous excitement and talk over the matter. Meetings were held in all the large towns. In the North the speakers called slavery the greatest evil in the United States, and a disgrace to the American people.
In the South the speakers declared that Congress had no right to dictate to a state as to whether it should have slavery or not. But even in the South few really stood up for slavery. Almost every one acknowledged that it was an evil. But it was a necessary evil, they said.
In the House and the Senate there were great debates also. But at length an arrangement was come to. Missouri was admitted to the Union as a slave state, but in the rest of the Louisiana Territory north of the degree of latitude 36 degrees slavery was forbidden for all time. This was called the Missouri Compromise; compromise meaning, as you know, that each side gave up something. And in this way a quarrel between the North and South was avoided for the time being.
But it was only for the time being, and wise men watched events with heavy hearts. Among these was the old President Jefferson. "The question sleeps for the present," he said, "but is not dead." He felt sure that it would awake again and shatter the Union, and he thanked God that being an old man he might not live to see it.
In 1821 Monroe was chosen President for a second time and it was during this second term that he became famous throughout all the world. He became so through what is known as the Monroe Doctrine.
During the wars with Napoleon the King of Spain had been so crushed that he was no longer strong enough to govern his colonies. So one after another the Spanish colonies in America had declared themselves free and had set up as independent republics. But Spain of course was anxious to have her colonies back again, and it seemed very likely that the King would ask some of the other great powers in Europe to help him to reconquer them. Monroe however determined to put a stop to wars of conquest between the old world and the new.