Editor's note: This is the third article in a five-part series honoring Women's History Week

When Elizabeth Blackwell and Mary E. Walker were little girls, they did not have to worry about what they wanted to be when they grew up.

They could be only one thing: a teacher. Luckily, they refused to settle for that and aspired for something more.

In 1849, Elizabeth Blackwell broke all boundaries to become the first woman physician, changing the face of medicine forever, according to "Lives of Girls Who Became Famous" by Sarah K. Bolton. A short time later in 1864, Mary Walker was the first woman appointed to the post of assistant army surgeon.

"With grit and determination, they proved that women can compete with men on an unequal playing field," said Norman Gevitz, professor and chair of the department of social sciences at Ohio University's College of Osteopathic Medicine.

Born in 1821 in Bristol, England, Blackwell later moved to Cincinnati where she worked as a teacher to support her family after her father died. She worked in Kentucky for a short time but returned to Ohio - it was there that a chance encounter changed her life.

A friend told Blackwell about a treatment she had for a gynecological disorder. She told Blackwell that if a woman doctor had treated her, she would have been spared a lot of embarrassment. The idea of becoming a doctor intrigued Blackwell, and she began her journey into the field of medicine.

After many rejections, Blackwell was finally accepted into the medical school at Geneva College in New York State. When she graduated in 1849, she made history all over the world.

Mary Walker also chose a difficult path to challenge society's perception of women's abilities, according to "The International Dictionary of Women's Biography," edited by Jennifer S. Uglow. Walker graduated from Syracuse Medical College in 1855, but is probably most famous for her fight against woman's clothing. In a time when women wore tight corsets and ankle-length hoop skirts, Walker could be found in "bloomers" - long, full trousers. She later wore only men's clothing, something unheard of at the time.

Walker's dream was to be a surgeon in the U.S. Army, a place that wanted nothing to do with the young dress-reform advocate. Only in 1864, when the army desperately needed medical help did they hire Walker as an assistant army surgeon in Tennessee. A few months later, Walker was captured by Confederates while walking alone and was held as a prisoner of war for more than four months.

The list of firsts continued for Walker when in 1865 she became the first woman to win the Medal of Honor for bravery in combat.

Blackwell and Walker paved the way for women in medicine, but their missions are carried on today by women like Gail Rosseau, a neurological surgeon in Chicago. One of only 80 women in a field dominated by men, Rosseau knows first hand what it must have been like for these early trailblazers.

"I walk in and they look at me and say, 'when will the neurosurgeon be in,' and I say, 'you're looking at her.'" Rosseau said.

But the image of a woman doctor always has been a barrier to females who want to pursue a career in medicine, she said.

To help move forward, these women can look back to the struggles of those before them.

"A lot of people don't have a real sense of the history of medicine," Gevitz said "To understand where you are right now you have to have an appreciation of what came before you."