It wasn't until Duke walk-on Brennan Besser approached New York City on Tuesday, completing a cross-country bike ride to raise money for people with intellectual or developmental disabilities (IDD), that he reflected on what he'd achieved.

He didn't want the emotions attached to his fundraising effort, which included free basketball clinics at every stop, to disrupt the flow of his 3,400-mile trek.

Besser's 23-year-old sister, Jacqueline, has autism and is nonverbal with limited motor skills. She's also the inspiration for the political science major's effort with his charitable foundation "Walk On! America" to raise $1 million for people like her who demand vital resources that allow them to live fruitful lives.

Besser's family is working on a plan that will help Jacqueline when she leaves home. Besser is from Chicago, and in Illinois, public funding for members of the IDD community stops when they turn 21, a fact that prompted Besser to come up with the idea of a bike ride.

"We now are focusing on making sure that her future will be secured," Besser said. "And that, of course, brought into the conversation the fact that we're not the only family going through these types of challenges and trying to figure these things out. It was really like the perfect marriage of 'How can I raise awareness?' We have firsthand experience with my sister. We are part of the IDD community. How can I leverage this platform and really give back on a national level?"

According to the Walk On America website, Besser has raised more than $343,000 toward his goal. He said the funds will go back to organizations that support members of the IDD community.

Initially, he favored a cross-country run. He ran a mile in 5 minutes, 5 seconds when he was a sophomore at Duke, a mark he said is posted atop the program's all-time list in the weight room.

To test that idea, he awoke one morning before the trip and just started running. He wanted to see how much ground he could cover in one stretch. After covering 24.5 miles, nearly a marathon, he began to rethink his mission.

"Then I stopped on the side of the road, called my parents," he said. "I couldn't feel my legs. I said, 'You know what, I don't think running is going to work, but let's try to figure out what we can do to make this thing work.' Then the bike became the vehicle that would get me across the country. It would still garner some attention for the fact that it's physically challenging but would allow us to connect with as many people in as many towns as possible with the time frame I have before I have to get back to school."

His trek began in May on a balmy day in Seattle. He covered nearly 60 miles per day, traversing more than a dozen states while spreading his message about the IDD community.

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He met celebrities such as former Chicago Bears coach Mike Ditka. He posed for photos with Montana Gov. Steve Bullock. He spoke to locals at a small lodge in Wisconsin. He toured the White House. And Tuesday, he rang the opening bell at the NASDAQ stock exchange.

The senior, who's appeared in two career games for the Blue Devils, had the support of head coach Mike Krzyzewski and several of his teammates. Portland Trail Blazers guard Gary Trent Jr., a second-round pick in June's NBA draft, called and offered support, reminding Besser to "just remember who you're doing it for when it gets really challenging."

"Brennan has contributed in so many ways to our program, whether it be in preparation, spirit, or work-ethic -- he's a one-of-a-kind walk-on," Krzyzewski said in a statement in May. "I love him, and the spirit he brings is infectious on this team. Nothing he does surprises me, because almost everything he does is not about him. It's about his talents, his emotion and his effort to help others. This is a terrific thing that he's doing this summer and he'll accomplish so much for so many people."

Brennan Besser is a senior walk-on at Duke. Michael Berg/Icon Sportswire

Besser also credits a support team that included a family friend and Rachel Besser -- his sister, who owns a fashion line -- following him on the trip in a pair of support vehicles. A cousin helped, too. A project manager worked at the organization's home base in Chicago. A pair of Milwaukee-based doctors biked part of the trip.

He endured minor obstacles such as a broken chain on a rocky road and a popped tire on an uphill climb during another rugged stretch. The worst unfolded last week in Washington, D.C., when someone broke into one of the support vehicles and stole a camera his team had used to document the trip.

"We've been successful," Besser said. "But there are just things you can't plan for, and we have a good enough team here where we're just trying to adapt on the go."

Besser's mission goes beyond money. He also hopes to eliminate the stigma attached to the IDD community.

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Those with disabilities deserve to be embraced, not exiled. Besser said if people took more time to develop relationships with people in the IDD community, they'd learn that they share more similarities with them than differences.

At one stop at the Children's Hospital in Milwaukee, he spoke to members of the IDD community who've worked with a hospital-sponsored project to attain employment. One young man who is employed by the hospital told Besser to take a message around the country.

"He said, 'I would just want you to please tell everyone that all we want as a community is to be given the chance to prove that we can succeed, and if we're given that chance, we will.' I still get chills thinking about it because it was so powerful."

This is a blue-collar effort for Besser, who could have done less to shine a light on his cause. He's connected to one of the most successful programs in college basketball history and a network of athletes who've excelled within and outside basketball.

He could have called them all and just asked for a tweet or an Instagram post.

Instead, however, Besser chose the grueling bike ride so he could meet and connect with people face-to-face.

"Coach K uses basketball as a vehicle to teach leadership skills and life principles," he said. "And the bike ride, what I'm doing, is simply a vessel trying to raise awareness, and we have this million-dollar goal for this community. There are days that are tough, tougher than others. And that really helps me push through. ... I don't know if it has hit me yet that I've biked across the country."