Mertz grew up sailing[1] and a 1954 Sports Illustrated article describes her tenacity and how she encouraged junior sailors.
[7] Knapp was a four-time winner of the Mrs. Charles Francis Adams Trophy (1950, 1954, 1959, and 1963),[8] which placed her as the United States' women's national sailing champion in those years.
[2] She also won the Syce Cup trophy for the women's Long Island Sound championship eight times.
[9][10][11] Her first win came in 1938 where she sailed with her sister-in-law Dorothy Knapp, Sarah Baylis, and the 13 year old Aileen Shields who was the youngest competitor of the event.
As of 2021, the Allegra Knapp Mertz Trophy is awarded each year to the winning women's match racing team in the United States.