As a long time Florida resident I have seen many changes including the Orlando Sentinel's announcement of Disney World coming to Florida. I lived in Orlando at the time and it certainly caused quite a stir that day and for the next fifty years. There is no singular event in Florida's modern history that has had so much influence on the state, transforming Orlando from a sleepy central Florida town, to the number one tourist attraction in the world.
There are several other significant events that have shaped today's Florida.
The advent of air conditioning that allowed year around living in Florida.
The Cuban migration from Fidel Castro's revolution in the early 60's witch transformed Miami into an world class international city.
The establishment of the Cape Canaveral Space Center, later renamed to Kennedy Space Center after President John Kennedy.