Harper was born and raised in California to Scottish parents.[2]
Club career
Celtic
In September 2018, Harper signed with Scottish Premiership club Celtic after turning down a college scholarship from UCLA.[3] After 13 players were ruled out of the first-team squad due to COVID protocols, Harper made his professional debut, appearing as a starter in a 1–1 draw against Hibernian on January 11, 2021.[4]
New York Red Bulls
On March 5, 2021, it was announced that Harper joined Major League Soccer side New York Red Bulls on a transfer from Celtic.[5] On April 25, 2021, he made his debut for New York, appearing as a second-half substitute in a 3–2 loss to the LA Galaxy.[6]
On May 10, 2022, Harper made his first appearance of the season for New York, providing an assist to Zach Ryan in a 3–0 victory over D.C. United as the club advanced to Round of 16 in the 2022 U.S. Open Cup.[7] A few days later, on May 14, Harper helped New York to a 1–1 draw on the road against Philadelphia Union, assisting Luquinhas on the equalizing goal.[8] Harper started his first match for the club on May 18, 2022, and scored his first professional goal in a 3–3 draw with Chicago Fire FC.[9] On July 24, 2022, Harper scored and assisted on the winning goal for New York in a 4–3 victory over Austin FC at Q2 Stadium.[10]
During the 2023 season, Harper became a regular starter for New York at right-back. On June 23, 2023, he scored his first goal of the season in a 2–2 draw with Charlotte FC.[11] During the 2024 season, new coach Sandro Schwarz played Harper mostly as a right-winger. On May 11, 2024, he scored his first goal of the season in a 4–2 victory over New England Revolution.[12] A few days later, on 15 May, Harper scored the winning goal for New York in a 4–1 victory over Atlantic Cup rivals D.C. United.[13]
International career
Harper is eligible to represent the United States and Scotland internationally. In 2019, he was invited to youth national-team camps for both nations, but decided to represent the United States.[14]