Nobody knows just how long the baby lay there that September night in 1986.

Someone had wrapped the newborn in a tan towel before placing him in a cardboard box and leaving it outside a thrift shop on Muldoon Road.

Around 9 p.m., an anonymous caller told 911 dispatchers there was a baby near a clothes donation bin outside the Salvation Army, the one just off the Glenn Highway.

Before police and ambulances could get there, two teenage boys out riding bikes in the fall twilight heard his cries. They looked inside the cardboard box, scooped the squalling baby up and cycled home with him.

The baby was still coated with afterbirth. His umbilical cord was clamped with the kind of plastic twist-tie used to secure a garbage bag.

"It was real young," one of the teenagers later told a newspaper reporter. "Not old at all."

At the hospital, nurses put a plastic identification band on the infant's wrist.

"DOE, Baby Boy" it read. "9-4-86."

For a few days, news of the baby in the box captivated Anchorage: It was in the newspaper, on TV and on the radio. There was so much interest, the baby's foster mother later told him nurses at the hospital had to keep eager well-wishers away.

Now that baby is almost 30 years old. His name is Benjamin Tveidt. He lives in Boise, Idaho.

It is time, he thinks, to solve the mystery of his birth.

'A special kind of loneliness'

Tveidt, a soldier in the Idaho Army National Guard, understands the chances he will find his biological parents are slim. But every time he fills out a medical history form that asks about his family with an "N/A," he wonders.

Knowing nothing about your birth parents "is a special kind of loneliness," he said. "It's hard to explain."

So for the last few years, Tveidt has been using a very modern method to seek his biological parents: DNA testing combined with the vast hive-mind of the internet's genealogists.

When Tveidt was deployed to Iraq in 2010, he heard about consumer DNA-testing kits. When the price hit an affordable $99, he bought one.

From a simple saliva swab he learned the basics about his own DNA: He was of European ancestry, mostly British.

"In one minute it was more information than I'd ever had about myself my whole life," he said. He also learned he could post his DNA profile on a website and possibly be matched to people who were genetically related to him.

He quickly found two distant relatives: Janice Johnson, a retired geneticist and amateur genealogist who lives in Newbury Park, California, and Juanita Genness, another retired hobby genealogist from Maine.

They are both fourth or fifth cousins of Tveidt, meaning they have a common ancestor several generations back. Together, they've constructed family trees using partial DNA matches as well as traditional genealogy.

They have even found what appears to be a genetic relative with links to Alaska just two generations back, though Tveidt isn't sure enough about that link to contact the man's descendants just yet.

"It's like trying to put a puzzle together but all the pieces are facing down," Tveidt said.

The life he was dealt

But DNA is one strand of his quest to find his parents. Putting his face and his story in the newspaper is another.

Tveidt is quick to say he's content with the life he was dealt.

A week after the teenagers discovered him, 'Baby Boy Doe' was sent to live with Verneta Wallace, a prolific Anchorage foster mother who has taken in more than 100 children over the past three decades.

Wallace was the one who named him Benjamin.

It was a lovely name, she thought, but it was also kind of a play on his unique circumstances: "It sounds bad, but Benjamin sort of sounded like 'bin,'" she said in a recent interview. "He was found by a clothes donation bin."

Baby Benjamin ate well, slept well, and charmed his foster family and their church congregation.

"You are without a doubt the very best baby we have ever had," Wallace wrote in a letter she sent with Tveidt when he was adopted and moved on to his permanent family.

Wallace kept detailed records. She knew her foster child would be moving on, but she didn't want his first six months of life to be a blank spot in his history.

She noted he had become something of a celebrity in Anchorage. Everybody wanted to know what had become of him.

The family of one of the boys who discovered him, Christian Chain, even kept in touch.They brought him baby booties and a rattle at Christmas.

Members of the Chain family couldn't be reached for this story.

"You will never know the impact you made on this town," Wallace wrote to baby Benjamin in the letter.

Wallace remembers the nurses at the hospital telling her a woman had called in tears asking about the baby.

Was it the mother?

"I really do think your birth mother loved you very much and just didn't feel capable to care for you," she wrote.

She believes that today.

"She wrapped him up in a towel. She cut off his little umbilical cord," Wallace said. "She didn't throw him away."

A childhood in Idaho

At six months old, the baby was adopted by an Army couple stationed at Fort Richardson.

He became Benjamin Tveidt.

The Tveidts lived in Alaska for three years, until moving on to another duty station and eventually to rural Idaho.

Tveidt spent his formative years in the communities of Mountain Home, a far-flung exurb of Boise, and Bruneau, a town in the arid, sparsely-populated southwest corner of Idaho. Ranching country.

He grew up playing in the hills, "doing country stuff" and spending time with his family, which by then included two sisters who are the biological children of his adoptive parents.

Until he was 11 years old, he had no idea he was adopted.

He learned the truth about his origins on a drive to Boise with his father. They were going to see "Mortal Kombat" at the movie theater for his birthday.

The story his father told him knocked the wind out of him. He was adopted? Abandoned? In Alaska?

He remembers his mom telling him not to tell the kids in school about it. She was trying to protect him, he knows. But it made him feel like there was something wrong with him.

He was a restless and rebellious teenager, leaving high school in the 10th grade. At 18, he joined the Idaho Army National Guard as a way to support himself and pay for college. He became a gunner for Bradley fighting vehicles, deploying twice to Iraq. He went on a disaster relief mission to Louisiana after Hurricane Katrina.

Right now he's single, focusing on work and college. He's earning an associate degree in political science. He thinks law school or study in international relations might be in his future.

"I've had a pretty decent life. Not always the best," he said. "But I may have had a very different life if they had chosen to keep me."

'I just want to know my place in the world'

Tveidt says he isn't angry with his biological parents. He knows they may be dead, or burdened by shame and guilt from the abandonment. His father may not know of his existence.

He understands nobody gives birth and leaves a baby without a major crisis.

Today, Alaska law allows mothers to safely surrender infants they feel they cannot care for at fire stations or hospitals. Back then, nothing of the sort existed in Anchorage.

Tveidt is prepared to fling the most intimate details of his life history into the universe and get nothing in response.

But he is a curious person, always has been.

"I just want to know my place in the world," he said.

And the questions only swell as he gets older: How a baby found in a cardboard box got there, and why.

Email Michelle Theriault Boots at mtheriault@alaskadispatch.com.