At only ten years old, while running with her parents, Patrick and Denise, she was spotted as a potentially remarkable talent by her coach-to-be, Brian Diglio. She has a brother Patrick, two years older, who was also a successful cross country runner while competing for North Rockland High School. Their brother Ryan is six years younger than Katelyn.
Competition
Encouraged by her family, she began setting age-group records in the 7th grade, retiring marks set by earlier high school phenom Mary Cain. In 2018, Tuohy's remarkable potential had fostered New York Times speculation on her future. Diglio, who is also her advanced placement U.S. History teacher, has endeavored to keep Tuohy in check while guarding her progress. “My role so far has been to try to put the brakes on, so she doesn’t do too much,” he said. “She has an unbelievable work ethic; I’ve never seen anything like it." He feels her academic diligence is as important as her athletic accomplishments. She finished the 2017–18 school year with a 4.59 GPA.
2017
Tuohy first took 32 seconds off the historic Van Cortlandt Park course record, during the Manhattan XC Invite, in the Bronx, New York, with 13:21 for the 2.5 mile/4 kilometer event. Then she won the 2017 Nike National cross country championship as a sophomore, to cap an undefeated season. With a 5,000 meter time of 16:44.7, she won by 40 seconds, trimming 12 seconds off the course record, despite cold and muddy conditions. The Rockland County legislature honored her victory, declaring December 19, 2017, as "Katelyn Tuohy Day." Tuohy competed for the North Rockland High SchoolRed Raiders. She became the fastest US outdoor high school 3,200-meter runner of all-time, running 9:47.88.
2018
On January 20, 2018, Tuohy also set the U.S. national junior and high school indoor 5,000-meter record, when she ran 15:37.12. In May, 2018 she became the fastest US outdoor high school 3,200-meter runner of all-time, running 9:47.88. Her 9:09.71 for 3,000 meters, run in June 2018, is the second fastest U.S. outdoors time ever in the country by a high school girl. On June 17, 2018, at the New Balance Outdoor NationalsTrack & Field championships in Greensboro, North Carolina, Tuohy won the mile by over 15 seconds breaking Polly Plumer's 36-year high school outdoor mile record with a 4:33.87. On September 22, 2018, at the Ocean State Invitational, Tuohy ran the fastest American girls cross country 5K ever with a time of 16:06.87, lowering the course record by 88 seconds, and leading her team to victory. Her time clipped almost 17 seconds from Katie Rainsberger's 2016 best-ever high school girls' standard on any course, running faster than all but one of over 1,000 high school boys running the sandy course, that day. On October 19, her 16:45.4 broke her own Bowdoin course record, set in 2017 while winning the state federation championship. The next fastest girl ran 19:07.9. On November 23, she won the 5K New York State XC Championship/Nike NY Regionals, in 17:14.0, by over 40 seconds. On December 1, 2018, despite her missing her state section championship race with knee tendonitis, a few weeks earlier, she repeated as Nike's Cross Nationals Individual Champion. Notwithstanding muddy conditions, she set a new course record time of 16:37.8.
2019
On January 26, 2019, in New York City, while finishing third in the 3,000, against seven pros, she broke Mary Cain's high school indoor record with 9:01.81. That gave her four of the fastest eight ever indoor times by a high school girl for the distance. On March 10, also in NYC, competing in the New Balance Indoor Two Mile, her 9:51.05 for first place made her the second fastest ever U.S. high school girl, indoors or outdoors. She also ran 2:48.77 for 1,000 meters, indoors. Discussions with her coach, Brian Diglio, regarding her continued representation of her North Rockland high school were reported to have been about her anticipated continuation of running for the school through the 2019 cross country and possibly the beginning of the indoor track season. It was thought that experiencing stiffer competition from professional runners might be expected to benefit her regarding the possibility of Olympic Trials training to follow in 2020. Diglio indicated it would be her choice to make. Despite feeling ill, on June 7th she repeated her 2018 state 3,000 meter title with a 9:21.9, 15 seconds in front of Chmeil. Due to her academic workload, allergies and an intense track schedule, Tuohy, conferring with her family and coaches, chose to end her outdoor season in early June, and anticipated returning to competition at cross-country in the fall. In her first major race of the season, Tuohy won the Great AmericanCross Country race in North Carolina, 13 seconds under the course record. On October 12, she won the Manhattan College Cross-Country Invitational elite Eastern States race in 13:33.2 on the 2.5-mile Van Cortlandt Park loop, missing her course record but winning by 12 seconds. On November 16, Tuohy won her third consecutive New York State cross country championship in 15:36.5 on a course that was snowy and slushy in parts. On November 29, she repeated as the Nike New York Regional qualifier, running 17:06.6 on the Bowdoin course, more than 20 seconds in front of runner-up Claire Walters. On December 7, 2019, Tuohy became the first athlete, boy or girl, to become a three-time NXN champion. She won the race in 17:18.4. This was the closest margin of victory for not only Tuohy but in NXN history. Beavercreek, Ohio's racewalking record holder Taylor Ewert finished second in 17:19.1, and Sydney Thorvaldson of Rawlins, Wyoming was third in 17.19.4. Ewert and Thorvaldson had closed a substantial late-race gap on the chilly and muddy course.
Honors and awards
During her sophomore year in 2017–2018, she won both the Gatorade Female Cross Country Player of the Year award and the Gatorade Female Track & Field Player of the Year award, making her the first athlete ever to capture the award in two sports, then she won the overall Gatorade Female Athlete of the Year award. Her photo was on the cover of Sports Illustrated that summer. In October 2018, she was honored as the Track and Field News High School Girls Athlete Of The Year. In 2019, she repeated as the Gatorade female cross country awardee for her undefeated 2018 season. Track and Field News named her as 2019's repeat "Indoor Girls Athlete of the Year". After winning the Nike Girls Cross Country Championships in Portland, Oregon, in 2019, she was again named the Gatorade Player of the Year, matching track star and future Olympian, Marion Jones as the only other such three-peat winner. The Gatorade award also factors in academic performance. Tuohy is an A student, destined for North Carolina State University.
