Hi A.-
I was born and adopted in 1978 (closed adoption as well). I found my birth mother about 10 years ago. Searching is hard. I'm not saying that to discourage you- I'm just letting you know. I totally understand the feelings and the wanting to know things. Okay so here are some things I learned during my search:
1. You could hire a private investigator but it will be expensive. And sometimes they don't find anything but you still would have put out that money.
2. Unless your bio mother has given consent there is NO way the hospital you were born at will give you any information. Privacy laws for one and it would indicated on the bio mom's file (if they still have it- they aren't required to after so many years) that you were given up for adoption so if they still had any records on you they would be sealed- only to be opened by the bio mom or a court order.
3. I'm sure you know this but your birth certificate is your amended one. Which means it has your parents (the ones that adopted you) info on it. There is no other birth certificate. The one issued when you were adopted- that's it. The thing about the birth certificate is that if the doctor who delivered you name is on there you may have a small chance of contacting him and convincing him to give you any info (if he remembers and is alive). Sometimes when they are retired (which is possible given he was practicing 40 years ago) docs get a little less rigid about privacy laws. It's worth a shot.
4. You could start by contacting the center- if they are still in existence. Most likely you are going to hit the same privacy/ sealed stuff as the hospital. Slight chance that the agency may have info on you bio parents and they can contact them to see if they want you to have their info. Very slight but back then there were no open adoptions- girls were expected to have the baby and then just go on with their lives, esp. if they were teens- for the most part that is. Anyway- sometimes a bio mom (or dad) would ask the agency to make a notation on the file that they would want to be contacted if the child ever searched for them. But it was fairly rare.
5. First thing I would do is register on some search websites. There are ones geared towards adoption. You put whatever identifying info you have on you and bio parents and then if there is a match the site will contact you (this is how I found my bio mom and found out I had a half bio brother- that I'm still searching for). Or if someone who is on the site recognizes the info and contacts you or the site to go to the next step.I don't have names of websites I used handy but I can get them and pm you either tomorrow or Monday.
6. Do your parents have the petition or the decree? Usually they blacked out all identifying info for the other party but sometimes they miss stuff (my older sister's decree- they left everything- bio parents names, address and phone number at the time of adoption, and extra info such as they had several other children at home. Made me crazy she had all this info and no desire to find them and I wanted to find mine SO bad and EVERYTHING was blacked that said birth anything. The papers were more black then anything. They even accidentally blacked out some of my dad's (adopted) info- got a little to black marker happy I guess). Anyway- there may be a docket number or other things on there that you can use.
7. You can access the vital records for the county where you were born- it costs but you can do it- and cross reference it with the info you have (your dob, hospital name, etc) and you can get a hit.
That's all I can think of now. I can go and find my notebooks from my search for my bio mom in the next couple of days and give you some more ideas. Good luck to you. Prepare yourself for it to possibly to take some time. Most of the time it's not something that happens quick. Also make sure you have a support system. It's a very emotional journey. Your feelings will be all over the place. If you decide to search decide what you want out of this (a relationship; just to know the info,one meeting, etc) before you start but know just because you want it one way doesn't always mean that's the that it is going to happen. And your feelings about what you want may change mid search. I'm not trying to sound depressing or condescending but it can be hard to remember those things when you are immersed in a search.
If you want to talk about any of this or have questions (now or if you decide later to search) feel free to pm me. I have been through searching three times now (my bio mom, the guy I thought was my bio dad- that's quite a story!, and my bio half brother- which I am still searching for on and off). And I can pm you in the next couple of days with the info I mentioned.
Good luck.
A.