What was the most significant result of the ruling in Marbury v. Madison?

Question

What was the most significant result of the ruling in Marbury v. Madison?

Answer 1

It was the first time that the Supreme Court ruled that a Congressional Act was unconstitutional, thus establishing the principle of Judicial Review.  This is one of the Checks and Balances that is written into the Constitution which helps control the three primary branches of the Federal Government.