Brannigan was a two-time national champion at
Northport High School, winning the individual crown in the 2-mile race as well as the
anchor leg of Northport's winning 4 x 1-mile team at the
New Balance Nationals Outdoor championships in Greensboro, N.C. in June 2014 (see: The Northport Observer, 6/19/14 and 6/26/14 editions). He was a six-time National H.S. All-American (see: The Northport Observer, 3/19/15 edition). Brannigan was not allowed to compete at the collegiate level because he could not meet
National Collegiate Athletic Association (NCAA) academic standards, due to
autism. He announced he would compete as a professional prior to his June 2015 graduation from Northport High School (see: The Northport Observer, 5/7/15 edition). He competed at the
2016 Summer Paralympics in the men's 1500-meter race, winning a gold medal. He finished fourth in the 1500m at the
2020 Paralympic Games in Tokyo in September 2021 (see: The Northport Observer, 9/9/21 edition). He won the bronze medal in the 1500m at the
2024 Summer Paralympics in Paris in September 2024 (see: The Northport Observer, 9/12/24 edition). == Personal life ==