Castonguay, a high school senior at the time, joined the sport simply because her parents told her it would "look good on college applications." This spontaneous decision would set her down a path that no college application booster could have predicted. 

After transferring to Saint Michael's College in her sophomore year, Castonguay joined the College's Nordic ski team, serving as the team's captain during her junior and senior years. She made her World Cup debut in biathlon for Team USA in December 2023.

Since graduation, Castonguay has continued to be a member of the U.S. National Biathlon Team and a competitor in the World Cup – and soon she may add the U.S. Olympic Team to her list of achievements. She is a rising contender for the 2026 Winter Olympics in Milan to compete in biathlon.

The beginning of her ski career 

Though Castonguay did not grow up skiing, she was competitive from an early age. 

"I ran cross country in middle school and high school, and then, kind of on a whim, I took up Nordic skiing," Castonguay said.

A week after putting on those skis, she competed in her first race. 

"It was the most fun I'd ever had in an athletic competition setting," Castonguay said. This race prompted her to focus her time on skiing as her primary sport in her senior year of high school. 

Castonguay's biathlon participation began more unexpectedly. During the COVID-19 pandemic, while attending her first year of college at the University of Vermont online, she traveled to Utah. 

Castonguay was visiting her younger brother, a longtime biathlete, when a coach convinced her to join a practice session. At this practice, it was the sport's blend of meditation, precision, and endurance "that really made it stick," she said. 

"I went home from that practice really feeling motivated, and I literally remember saying to myself, I want to be really good at this," Castonguay said.

Finding a family at St. Mike's 

As her passion for skiing and biathlon grew, Castonguay transferred to Saint Michael's College in search of a better fit. At St. Mike's, Castonguay was a member of the Nordic skiing team while also training for biathlon.

"I didn't have to put biathlon on hold to get my college degree," she said. "A lot of my peers and teammates postpone college because they just can't really figure out a way to pursue academics and athletics at a high international level." 

Castonguay credits former Nordic skiing head coach Molly Peters, along with her economics professors, for helping make her dream a reality. 

"All my professors were extremely supportive, encouraging, excited for me, and allowed me to tune into class remotely, or get notes, and really, just went out of their way to work with me and be accommodating," Castonguay said. 

Castonguay specifically recognized Samantha Trajkovski, Assistant Professor of Economics and Castonguay's senior thesis adviser, as especially influential. Castonguay wrote her senior thesis while in Italy, traveling for the World Cup, meeting with Trajkovski over Zoom.

"She helped me fast-track my thesis time, and I'm super appreciative of her being so accommodating of that," said Castonguay.

The Nordic skiing team played a major role in Castonguay's experience at St. Mike's. 

"The ski team is a really great program," said Castonguay. "The team was really supportive of my biathlon career, and it just feels like a family."

A rise in her career 

Despite entering the biathlon sport later than most, Castonguay's progression has been fast. She first qualified for international competition during an unexpected win at a senior-level trial race. This win marked Castonguay's first major biathlon breakthrough. 

From there, her accomplishments have quickly stacked up, including being Junior World Championships competitor, making her World Cup debut at 22 years old, being named to the U.S. National Team in the spring of her senior year at St. Mike's, and making her World Championships debut in 2024. 

"I feel very thankful that it's been like such a very clear stepping stone ladder of upward trajectory," she said.

Now that Castonguay is deep in preparation for the Olympic trials in January, this achievement feels more and more in reach. 

"We have a really we have a really strong women's team, and I think we're all very close in abilities," Castonguay said. "So on the day that we have our trials races, it really could come down to anyone's race that day."

Until then, Castonguay will continue training for the possibility of Milan – but first, she'll compete in the International Biathlon Union Cup in Austria. 

"If I was to make it to the Olympics, it would really serve as a … really good cherry-on-top moment, because there's a lot of people in my life that allowed me to get where I am today," Castonguay said.