Rockets were being made long before 50 years ago. There were plenty of rockets in WWI. And there were smaller rockets going back to before the US war of independence (ie "the rocket's red glare"). If we are talking big metal things that fly into space being produced on an assembly line, then those operating in Germany during late WWII making the V2s (75years ago) were probably the first rocket factories. But I'm not going to clap for them.