The framers designed the constitution so that no single section deal's directly with federalism. Instead, the division of powers between the states and national government appears throughout the constitution. The constitution ensures that no branch of government can act independently, and yet no branch depends on an other.
They divided the powers between the states and national government so that they keep each other in check. The states and national government have their own separate powers but they do have concurrent powers as well. Article 1, section 8, gives a list of enumerated powers of the Congress, which is followed by a clause that gives Congress the power to make all laws necessary and proper to carry out its power. National power is also based on the Supremacy Clause (Article VI), which says that the constitution and laws made under its provisions is the supreme law of the land. Article 1, section 9 lists powers not granted to Congress along with the first ten amendments (Bill of Rights) limits the power of the national government over individuals.
The constitution says less about the powers granted to the states. The tenth amendment says that all powers not given to the national government are reserved for the states. The states are given the power to approve the constitution itself and the amendments to it. Article 1, section 10, denies the states certain powers. Amendment fourteen limits the power of the states over individual liberties.
The relationship between the states and national government has changes since 1787 due too changes that have happened over the years. The role given to the supreme court to step in and interpret what it thinks the constitution really means when there is conflict about which level of government should have final say on a given issue.