On Friday, Terra McKean posted a photo of herself holding poster a with information about the sister who was put up for adoption more than 33 years ago.
"Please help me find my sister," the poster said. "Please like and share."
Her mother, she said, was a young, single parent in 1980 and felt she couldn't care for a second child. So she turned to adoption.
McKean, who came along three years later, spent years wondering what happened to her sister. She went through official channels and tried internet searches, but nothing paid off until her Facebook post.
In less than two days, her photo had been shared 13,000 times and she had received hundreds of messages from around the planet.
McKean said she was overwhelmed, but one message in particular took her breath away.
"I just open it and start reading," she said. "It's kind of like, 'Hey, I have some information, you have some information,' and then it's like, 'I'm your sister!'"
After she got over her shock, she connected online with her sister. They spent hours talking on the phone Saturday night.
"It's like making a new friend," she said. "Except I'm extremely nosy and I want to know everything about her."
McKean said she will speak to her sister again soon and hopes they can one day meet in person.
She's seen the woman's photo and says the resemblance to their mother is striking.
McKean said she will not disclose her sister's name or location — for privacy reasons and to allow her the chance to tell people herself.
One surprise that came about is that the two sister have met — they once lived in the same city together.
"We've seen each other in our lives."
McKean said she's filled with happiness to finally get answers, but also to learn that her sister is happy, too.
"She's had a good life," McKean said. "She had good parents that raised her well with good values."