Looking for Baby Girl born 4/1971 in PA

Hi my name is Shelly Cropper, I am looking for my half sister whom my mother gave up for adoption at birth. The only information I have is that she was born toward the end of April in 1971 in Pennsylvania, not sure of what hospital, but I'm quite sure it won't be far from Mechanicsburg which is where my mother stayed with her sister when she went into labor. Any information you may supply that could help me in my search would be greatly appreciated. My mother's legal last name at that time was Cropper, but she may have went under her maiden name of Sullivan her first name was Gail. Just wanted her to know that she does have family out here that would love to meet her if she was interested.