CRADLE: Looking for sister b Nov 9th 1964

My mother, Barbara, gave birth to a girl on Nov 9th 1964 at the Edgewater Hopital In Chicago. My sister was then adopted through the Cradle. My mother has spent years looking for her -unsuccessfully. I am beginning to search myself and am not sure how to go about it. If any one has any advice, it would be much appreciated. I can be reached at jxido@cabula6.com thank you Jeremy