You guys realize that Bill Bowerman was a consultant to Asics (or Onitsuka tigers back then) in the late 60's and early 70's?
He designed the shoes and ordered them from Asics, once they couldn't supply enough and started messing up the orders he made his own company Blue Ribbon Sports and took the designs he made. Eventually Asics sued him and Bill won the suit, gaining rights to the shoe design and some money for damages.
But to answer the original posters question, yes i do believe the Nike Cortez was the first real nike product that boomed.