The Constitution created a Union. That Union was of the several States, and the Constitution was written to join those States into a confederation, with a federal government that dealt only within the powers and authorities defined in the document. The autonomy of states was assured within the Constitution, though doubts arose as to whether the federal government might attempt to secure more power than was intended and granted to it.
The most significant clarification of that intent was laid out in the Preamble to the Bill of Rights. A preamble sets forth the purpose of a document, and that which was ascribed to the first ten Amendments reads, as follows: