Who was the first woman to run a mile in under four minutes and twenty seconds?

Mary Teresa Slaney (formerly Tabb, née Decker; born August 4, 1958) is a retired American middle-distance runner. During her career, she won gold medals in the 1500 meters and 3000 meters at the 1983 World Championships, and was the world record holder in the mile, 5000 meters and 10,000 meters.

In total, she set 17 official and unofficial world records, including being the first woman in history to break 4:20 for the mile. She also set 36 US national records at distances ranging from 800 meters to 10,000 meters, and has held the US record in the mile, 2000 meters and 3000 meters since the early 1980s, while her 1500 meters record stood for 32 years. In 2003, she was inducted into the National Track and Field Hall of Fame.

Decker was the first woman to break the 4:20 barrier for the mile in 1980 when she ran it in 4:17.55. However, this time was never ratified by the IAAF (International Association of Athletics Federations). In 1981 she married fellow American distance runner Ron Tabb. The couple divorced in 1983. In 1982, under the name Mary Tabb, she ran the mile in 4:18.08, breaking the official record of 4:20.89 by the Soviet Lyudmila Veselkova. This time was ratified.