Los Angeles (CNN) -- In his inaugural address, President John F. Kennedy posed a challenge to Americans: "Ask not what your country can do for you; ask what you can do for your country." Just a few weeks later the Kennedy administration provided a vehicle for young Americans to undertake that challenge.
It was in March 1961 that the Peace Corps was established. In the 50 years that have followed, more than 200,000 volunteers have entered the Peace Corps, serving in 139 countries throughout the world.
"I wanted adventure," says Robert Spich, 66.
He was among the first generation of Peace Corps volunteers. He served in a remote village high in the Chilean Andes.
"I remember getting out of the bus," Spich recalls, "It was a rainy day and dark. I remember I thought, 'Two years? Here?'"
Spich actually labored for three years before returning to the United States. He helped build a school, organized a reforestation program and designed a portable sheep bath that could be pulled by oxcart from village to village.
"Sheep were fundamental to life there," says Spich.
His wheeled contraption helped keep the flocks healthy.
A generation and 100,000 volunteers later, Anne Rimoin set out for the West African country of Benin. In the 1990s Rimoin was a 22-year-old history major and an intern at a Hollywood record company.
Rimoin was headed toward a career as an entertainment lawyer. But then she was sidetracked by the Peace Corps.
"The Peace Corps completely changed everything in my life," Rimoin says. "It changed who I was. It changed my perception of the world, and my perception of what I could do in the world."
Rimoin found herself battling a water-born disease called guinea worm.
"Guinea worm is a disease that is very painful," says Rimoin. "My job was to teach people how to identify cases, to treat people who had it and how to prevent it from transmitting to somebody else."
Like most Peace Corps volunteers, Rimoin found the living conditions challenging.
"I lived in a village that didn't have electricity, didn't have running water, the conditions were very Spartan."
But like most Peace Corps volunteers, Rimoin coped with the difficult circumstances.
Adriana Publico is a Peace Corps volunteer of the 21st century. Her assignment took her to Mauritania, on the edge of the Sahara Desert.
"Life expectancy there is about 52," Publico says. "Life there is very tough."
Her job involved teaching English and involving Mauritanian girls in after-school programs.
"In Mauritania girls typically go to school until they are about 15," says Publico. "It's about exposing young women to the idea they can have a career or go to college."
It is an uphill battle in a country with few educational resources, Publico found. "No children had books. Their teacher wrote on the blackboard and that's all they got. And the blackboard was just painted on the wall."
Publico says the school building where she worked did not have glass in the windows. Education is a major theme for Peace Corps volunteers. Spich helped build a village school in the Chilean Andes in the 1960s.
In the 1990s, Rimoin paid the tuition for a young peanut vendor who lived in her village. She believes that kind of one-on-one outreach is what makes the Peace Corps so effective.
"You are not affecting population change in the Peace Corps," she says, "you are affecting people individually because it's all about your individual contact with people."
For many volunteers, the Peace Corps becomes a life-transforming experience. Since serving in Benin, Rimoin has gone to work for the World Health Organization tracking some of the world's most dangerous diseases, including monkey pox, hemorrhagic fever and Ebola.
She works in the jungles of the Democratic Republic of Congo.
She says the Peace Corps, "Challenged me to think beyond myself. To think about other people."
"It changed my whole life," says Spich.
He teaches economics at UCLA and consults on issues of Third World development.
"I carry it with me wherever I go," agrees Publico.
She is studying for an MBA, hoping to use business skills to make life better in the poorest corners of the globe.
Together the three volunteers span a half century of Peace Corps efforts around the world.