On Thursday, the Nixon sisters were pretty tired. They had just returned from Washington D.C. after getting fourth place in SourceAmerica's Design Challenge.

“The whole aim is to create some kind of invention, some kind of tool, to assist people with disabilities,” said 15-year-old Namitha Nixon.

“Honestly we didn’t even expect to finish when we first entered the competition. We kind of just did it on a whim. So it was just amazing that we even got to go to DC in the first place,” said Anna Nixon, who is 17 years old.

SourceAmerica is a nonprofit that helps create employment opportunities for people with disabilities. More than 120 college and high school teams entered the competition.

First, the young ladies teamed up with a local nonprofit, the Edwards Center.

“They basically provide job opportunities, work training, housing for people with disabilities,” said Namitha.

They toured the facility, found a workflow problem, and figured out a way to fix it. In this case, they saw the process of bundling boxes required two people: one employee and one staff member. That left workers often waiting for help.

“We wanted to solve that. We made a little packaging machine which is really simple to use. You just stick five boxes in a rotating container and it just spins it up and wraps the boxes together and then you just cut it and take it off. So now they can do it all by themselves,” said Anna.

The sisters, along with their dad, also founded the nonprofit STEM4Girls.

“Over the past three years we’ve been able to reach over 500 students so it’s been pretty amazing. It’s grown really, really fast,” said Anna.

They hope to attract more young girls to careers in science, technology, engineering, and math. They’re all fields where men typically outnumber women.

“I think it's really important to break down those barriers especially at a young age,” Anna said.

Nandhana Nixon, 15, said STEM4Girls is all about empowering girls.

“A lot of the time they just don’t have the opportunity to learn more about it or participate in programs about it because they’re not surrounded by other women who they can work with,” she said.

As for the competition, the girls said it wasn’t about winning.

“What really struck us about it is it was actually using the skills we have to give back to someone who really needs help,” said Nandhana.

"It doesn't really take that much to be able to make a huge difference,” said Anna.

The Nixon sisters say they’re planning to enter the competition again next year.

A team from Catlin Gabel got third place in the competition. They designed an app to help people with disabilities in the workplace keep track of their tasks.