My brother-in-law was adopted at birth in New Jersey.
He found a lawyer, went to court and it took almost three years before the adoption records were opened. I'm going back to about 30 years ago when he did this. However, it should be easier now because the precedent has been set. Don't let anybody tell you it's never been done.
My brother-in-law was the second person in the State of NJ to have his adoption records opened. The first person to do so is a woman.
By the way, the son of the brother-in-law I am speaking of adopted a child at birth two years ago and the adoptive parents were given all the details of the birth.
My brother-in-law is estranged from my family so I can't tell you any specific details.
Good luck!