After the Constitutional Convention created the new Constitution, it still had to be ratified. Not everyone actually liked the new document. The Antifederalists felt that it gave too much power to the federal government. The Federalists, therefore, had to make some compromises to get the Antifederalists to agree to the Constitution.
One compromise that they made was to list the things that Congress could do. Article I of the Constitution lists which things Congress can do, which means that the national government could not simply do whatever it wanted. This meant that the states would have some powers reserved for them.
The main compromise, though, was to create the Bill of Rights. The Antifederalists worried that a strong national government would abuse their rights in the same way that the British government had. To allay their fears, the Federalists agreed to create the Bill of Rights. These amendments to the Constitution spelled out what rights the people had that the national government could not interfere with. For example, it said that the national government could not infringe on people’s rights to freedom of speech or religion. The Bill of Rights also said that any rights not given to Congress or taken from the states belonged to the states. This helped ensure that the states would have some powers of their own.
The main compromises, then, were ones that made sure that the states would be guaranteed to have some powers and that the powers of the federal government would be limited.