SEATTLE — For four years on Mercer Island, Stanley Ann Dunham impressed her high-school classmates with a wickedly sharp wit. She was an "intellectual rebel" with a fledgling beatnik sensibility that would eventually take her around the globe.

But shortly after high-school graduation in 1960 she vanished from the Seattle area, and would have been little more than a foggy memory to most — if not for a son she had just a year later: Barack Obama.

Now that Obama's unique personal history has become part of his rising political profile, his mother's formative years in the Pacific Northwest are a little-noticed chapter. Even Obama glosses over the chapter in a single line in his best-selling biography.

Dunham, who died of ovarian cancer in 1995, is described as the "most dominant figure" in Obama's life. Obama's half-sister says Dunham remembered her teen years on Mercer Island so fondly that she wanted to attend college in Seattle. Instead, her parents took her after high school to Hawai'i, where Obama was born.

"Her life showed a deep respect for intellectual rigor and perhaps an uncommon sense of learning," said Obama's half-sister, Maya Soetoro-Ng, who lives in Hawai'i.

Now that Obama is leading the fight to become the Democratic nominee for president, Dunham's classmates are remembering her again. In the Eisenhower era of poodle skirts and Ozzie and Harriet, she preferred jazz, refused to baby-sit and viewed education — not marriage — as the key to her future.

Few of them saw Dunham after she left for Hawai'i. But they still see much of her in her famous son: her eyes, her chin, her broad-minded globalism, her intellectual rigor.

"You see her in his expressions, how he handles adulation," said Marylyn Prosser of Ketchum, Idaho, a former classmate. "I get a sense he is grounded, and that reminds me of his mother."

As Obama has climbed the political ladder, one particular anecdote about his mother is repeated: that her father, Stanley Armour Dunham, Obama's grandfather, gave his only child his first name because he wanted a boy.

Stanley Ann went to elementary school in Kansas before her father, a smooth-talking salesman, moved his family to Seattle in pursuit of work. The Dunhams moved to Mercer Island in 1956 to get their daughter into the newly opened high school there.

Stanley Ann Dunham's classmates, many of whom had lived on the island their whole lives, viewed Dunham as a novelty.

"She had a really ironic sense of humor, sort of downbeat, and she was a great observer," said Iona Stenhouse, of Seattle, a former classmate. "There was an arched eyebrow, or a smile on her face about the immaturity of us all. I felt at times that Stanley thought we were a bit of a provincial group."

Said former classmate Chip Wall: "She was not a standard-issue girl. You don't start out life as a girl with a name like Stanley without some sense you are not ordinary."

She was drawn to a wing of Mercer Island High called "anarchy alley." Jim Wichterman taught a wide-open philosophy course that included Karl Marx. Next door, Val Foubert taught a rigorous dose of literature, including Margaret Mead's writings on homosexuality.

Dunham thrived in the environment, Wichterman said.

"As much as a high-school student can, she'd question anything: What's so good about democracy? What's so good about capitalism? What's wrong with communism? What's good about communism?" Wichterman said. "She had what I call an inquiring mind."

She also showed her politics, wearing a campaign button for Adlai Stevenson. And despite flirting with atheism, she went to services at East Shore Unitarian church, a left-leaning congregation in Bellevue.

As graduation neared for the class of 1960, Dunham had hoped to join many of her classmates at the University of Washington, and was also accepted to the University of Chicago, according to Obama's memoir, the best-selling "Dreams from My Father."

But her father was restless. He found sales work in Hawai'i. He insisted his daughter, who wouldn't turn 18 until November, attend the University of Hawai'i, Soetoro-Ng said.

Dunham hadn't had a boyfriend in high school, according to Maxine Box, her best friend at the time. So Box and others were stunned when Dunham wrote them to say she'd married the University of Hawai'i's first African student, a Kenyan named Barack Obama.

She gave birth to Barack Obama Jr. in August 1961.

"We could see Stanley, with her good grades and intelligence, going to college, but not marrying and having a baby right away," said Box, a retired teacher in Bellevue.

"I can't think of anything she said or did that would lead to such a radical thing. At that time, you practically crossed the street if you saw a black man and a white woman.

"Black and white didn't go together at that time."

Susan Blake, another high-school classmate, said that during a brief visit in 1961, Dunham was excited about her husband's plans to return to Kenya.

"We all had June Cleaver as our role models, and she was blazing new trails for herself," said Blake, a former Mercer Island city councilwoman.

The marriage was brief. By 1962, Dunham had returned to Seattle as a single mother, enrolling in the University of Washington for spring quarter and living in an apartment on Capitol Hill. But friends said she got overwhelmed and returned to her family in Hawai'i, and formally divorced Obama Sr. in 1964.

Over the next three decades, she became a well-traveled anthropologist, working in Indonesia, Pakistan and elsewhere.

"The life that Stanley chose to live after she left (Mercer Island) is indicative of the fact that Stanley thought about what else was out there," said former classmate Stenhouse.

"She was ready for having different experiences."