It was located throughout its existence at 44th and River Park Drive, in the Shawnee neighborhood of Louisville.

The school produced several notable members of the community, including Citizens Fidelity Bank president Daniel Ulmer, Rohm and Haas president Daniel Ash and University of Louisville trustee George Fischer.→ By the 1970s, the school was a victim of changing times, as white flight had seen what was once an all-white neighborhood become integrated and most Catholic families left for the city's southern and eastern suburbs.

In 2002 a museum containing Flaget photos and memorabilia was dedicated in the Alumni Building of Trinity High School.

However, Flaget became best known for its football program,[2] which compiled a 196–79–17 record from 1945 to 1973[3] Paulie Miller was hired in 1945 as the coach of various sports teams, but became famous as the coach of the football team, establishing St. X as their rivals and winning their first state championship in 1949.

The team won state championships again in 1952, 1958, 1961 (41–13 over Fairdale High School), and in 1967 under Norm Mackin (21–7 vs. Thomas Jefferson High School) and 1971 under Pete "The Computer" Compise (a 6–6 tie with Thomas Jefferson) after Miller had stepped down.