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I learned about my long-lost sister over burgers and fries at the Ground Round in Crystal. The year was 1994.

It was just Mom and me that night. I hadn't noticed her nervousness as we snacked on salty yellow popcorn. How she barely touched her food. I was 26 years old and concerned primarily with myself.

So I chatted away, oblivious to Mom's unease.

Finally, she took advantage as I was biting into my burger.

"Kim, there's something I need to tell you."

She took a breath.

"When I was about 20, before I met your dad, I got pregnant and had a baby that I gave up for adoption. You have a sister."

She paused, looking at me expectantly. I finished chewing and swallowed.

"Wow," I said.

"I've been in touch with her. She called me a couple of weeks ago. She lives in Michigan, but she's coming to Minnesota to meet everyone. Next month."

"Wow."

And by the way, Mom told me, her name is Kim.

Mom's news was neither angering nor disappointing, as she feared it would be. Mostly, I was surprised. Not just to learn I had a sister, but to realize I didn't know my mother as well as I thought. Turns out, she lived an entire life of her own before I entered it.

Who was this woman I called Mom?

Hidden away

Mom was one of a swelling tide of unwed women who became pregnant in midcentury America. She graduated from Spring Lake Park High School in 1957, the same year the baby boom peaked and the number of "illegitimate" births in the U.S. surpassed 200,000 for the first time.

Still, premarital pregnancy came with a hefty burden of shame. Mom got pregnant in the spring of 1960. Her erstwhile boyfriend having fled town, she spent months squirreled away in the half-story bedroom in her parents' house. She lived under strict orders not to show herself in public.

In early January 1961, my grandmother drove Mom to St. Paul to spend the last days of her pregnancy at the Salvation Army's Booth Memorial Hospital, one of three maternity homes for unwed mothers in the metro area.

For two weeks, Mom scrubbed floors and smoked cigarettes alongside dozens of other "girls in trouble."

On January 16, she gave birth to her first daughter. She counted her baby's fingers and toes, named her Lynette, then let her go.

She believed she was doing her baby a kindness by giving her to a happy, married couple. All the experts told Mom this couple could provide the kind of upbringing beyond the reach of an unwed mother.

A few days later, Mom left Booth with empty arms, her slate supposedly wiped clean.

For the next 33 years, she did not mention her daughter to anyone but my father.

Our growing family

My sister was named Kim by her adoptive parents. She reunited with Mom and met my Dad in early July 1994, then returned later that month to meet the rest of her Minnesota family. My younger brother, Eric, and I met her at Mom and Dad's house in Crystal.

We stared in wonder at the sister we never knew we had.

Turns out, Kim looks a lot like Eric and my mother's youngest siblings, with their fair hair and blue eyes. They stand out in a family of brown-eyed brunettes.

I tried to figure out how nature connected us and how nurture separated us. Kim and I share an edge of impatience, but she's a cat person and I like dogs. She likes to shop and I don't.

The next day, Kim met her aunts and uncles and cousins at a picnic at Lake Harriet. We spent the afternoon joking about Eric having two sisters named Kim before dusting off some old family photo albums. We hoped Kim would see herself in the blurry images of her forebears. We wanted her to know that her deep-set dimples and long legs weren't flukes of nature. They came from somewhere, from someone.

The reunion fulfilled decades' worth of yearning for Mom and Kim, but it was different for Eric and me. We hadn't spent our lives searching strangers' faces for hints of resemblance. Adding a bonus sibling was a pleasant surprise.

Then, in December 2006, my husband and I adopted a little boy from Vietnam.

Tu was 16 months old when we brought him from the steamy Mekong Delta to frigid Minnesota. He adjusted to this profound dislocation with relative ease, aided in large measure by the love my Mom showered on him.

For two precious years, until she died in early 2009, Mom was the doting grandmother every child longs for. She stocked her house with Tu's favorite toys, gave him his first taste of pop, brought him to his first movie.

I suspect there was something special about her relationship with Tu, knowing she was helping to raise another woman's lost child. I regret not asking Mom about this more directly when I had the chance. I'm also sorry I didn't ask her for every detail about her stay at Booth.

But that's not the way we were. We did not discuss deep emotions. We got on with things.

Still, Mom's experiences as a birth mother left a deep impression on me as an adoptive mother.

Every time adoption creates new family ties, it disrupts others. I was privileged to learn this lesson by observing the dynamic between Mom, Kim and Kim's adoptive parents. The experience helped me approach my position in our new transnational triad with a certain humility.

I know there will be questions I simply cannot answer for my son. I also know that somewhere in Vietnam a woman wonders every day about the boy she brought into the world.

Kim Heikkila is an oral historian and visiting assistant professor of history at St. Catherine University. Her first book, "Sisterhood of War: Minnesota Women in Vietnam," was a finalist for a 2012 Minnesota Book Award. She is working on a project that blends a history of Booth Memorial Hospital with her mother's story as a "Booth girl." Does your family have a connection to Booth? Contact her at kimheikkila68@gmail.com.

ABOUT 10,000 Takes: 10,000 Takes is a new digital section featuring first-person essays about life in the North Star State. We publish narratives about love, family, work, community and culture in Minnesota.