Implied powers, in relation to the U.S. Constitution, are powers not specifically given to the Federal Government of the United States. They derive mostly from the Constitution's Supremacy clause (Article Six, Clause Two).
The implied powers of the Federal government was a conception idea formed after Thomas Jefferson decided to go ahead with the Louisiana Purchase in 1803, although the Constitution did not explicitly give him the power to do so. Later, the implied powers played an important role in the court decision of McCulloch v. Maryland, with the Second Bank of the United States using the idea to argue the constitutionality of Congress creating it in 1816.