A member of Congress introduces a bill into his or her legislative chamber. The president may sign the act of Congress into law, or he may veto it. Congress can then override the president's veto by a two-thirds vote of both the House and Senate thereby making the vetoed act a law.
Once congress agrees to the new law, it goes through the president. He decides where it is created or not. If he does not accept, it is vetoed. However, if 3/4 of Congress decides to pass the law after he vetoes it then it is passed.
Before Missouri joined the Union, the free and slave states were equally balanced in congress.Missouri wanted to join as a slave state, so the balance would be upset.
