This activity happens towards the end of the year or whenever you have covered about 100 years. The purpose of the activity is to engage students in an intellectual conversation amongst themselves to convince each other which event we had studied was the most important. These events can be altered depending on what was studied in class (my rule was it had to have happened on US soil so WWII in the Europe/Pacific, Korea and Vietnam were off the table). Students try to convince each other why their event was the most important. Different rotations are set up to engage the whole class and every student which have to be generated a bit on the fly depending on who is there and which groups you have. In the end student vote and each year the most important/influential event changes.