The new Hollywood movement brought us many filmmakers who are now house hold names. This includes,Woody Allen,George Romero,Martin Scorsesse,Francis Ford Coppola and the most well known of all,Steven Spielberg.
Starting out making tv movies, Spielberg made his theatrical debut with 1974’s Sugarland Express. The next year he would release the major budget masterpiece,Jaws.
Jaws though a horror film created the summer blockbuster type film we have today. While some would say the Godfather was the first block buster, that film had more in common with the classic 3 hour epics. Jaws had many tropes in common with block busters today such as high budget,over the top action,release in summer and big focus on special effects. This trend would continue with Star Wars,Raiders of the Lost Ark and many others including the big marvel films of today.
All and all this is how Jaws is the first blockbuster.