Implied powers, in the United States, are those powers authorized by the Constitution that, while not stated, seem to be implied by powers expressly stated. When George Washington asked Alexander Hamilton to defend the constitutionality of the First Bank of the United States against the protests of Thomas Jefferson, James Madison, and Attorney General Edmund Randolph, Hamilton produced what has now become the classic statement for implied powers. Hamilton argued that the sovereign duties of a government implied the right to use means adequate to its ends. Although the United States government was sovereign only as to certain objects, it was impossible to define all the means which it should use, because it was impossible for the founders to anticipate all future exigencies. Hamilton noted that the "general welfare clause" and the "necessary and proper clause" gave elasticity to the constitution. Hamilton won the argument with Washington, who signed his Bank Bill into law.
Later, directly borrowing from Hamilton, Chief Justice John Marshall invoked the implied powers of government in the court decision of McCulloch v. Maryland. This was used to justify the denial of the right of a state to tax a bank, the Second Bank of the United States, using the idea to argue the constitutionality of the United States Congress creating it in 1816.
In the case of the United States government, implied powers are the powers exercised by Congress which are not explicitly given by the Constitution itself but necessary and proper to execute the powers.