Hey there!
I chose the case of Marbury v. Madison
This case took place in 1803. It is considered one of the most - if not, the most - important Supreme Court cases, ever. It was the first time in history that the Supreme Court had proved that an act of Congress was unconstitutional - against the Constitution. This cased established an idea of judicial review - where the Supreme Court first got to decide whether a law that Congress was trying to pass was unconstitutional or okay.
Hope it helps and have a great day!
