Why is the McCulloch v. Maryland case important?

This case is important because it set up the idea that the
federal government can do more or less whatever it wants.  It set up a broad definition
of the power of Congress under the Constitution.

Before
this case, it was not clear what Congress was allowed to do.  There are very specific
things that the Constitution explicitly says Congress may
do.  These are called expressed powers.  But are these the
only things Congress may do?  This is the question
McCulloch decided.

In this case, the Supreme Court ruled
that the "elastic clause" is what we should pay attention to when deciding what Congress
can do.  It says Congress may do anything "necessary and proper" to carry out its
expressed powers.  In this case, the Court said that this clause allowed Congress to set
up the Bank of the United States even though the Constitution never says "Congress may
set up a bank."

So by ruling in this way, the Court said
that Congress can do whatever it wants as long as that is not
prohibited by the Constitution.  Big difference, right --
Congress can do anything unless the Constitution prohibits
it rather than Congress can do only what the Constitution
explicitly says it may do.