John Doyle
Ansys Employee

It is an interesting question, but kind of outside the scope of this forum.  You should conduct a study on Additive Manufacturing History.  There are many textbooks on the subject.  In general, I believe the first patent described it as Rapid Prototyping using plastics(late ~1970s).  Metal Additive was not introduced until early ~1990s.  I believe it was originally researched at Wake Forest and MIT, but there were probably other institutions and corporations researching this in parallel as well.