how do you go about finding a parent

I have some questions about this whole adoption prosess. I know my father but it is as if my mother droped from the face of earth.I know her name and I have her age but no seems to know her birthdate nor her ss#. I questioned the social surity office but I recived a long line of do this and thats. what is the best way to start looking? My moms family seems to be in total secrets about any info on her and my father well same thing. I would love to find just one person who can give some advice i can use. my grandmother adoped me and my siblings but she olny wanted that monthly check so I will never get the truth out of her. My father spent time in jail for a robbery that he and my mother commeted in 1977 and since then it has been all secrets about my mom. I need some help..... how do you go about finding someone who may have remarried or moved from the united states?