1966

Once again the Japanese runners made a shambles of the field as they convincingly swept the first four places. Japanese champion and pre-race favorite, Toru Terasawa was upset by countryman Kenji Kimihara, who came from fourth in the last two miles to grab the victory wreath in 2:17:11. Although women would not be officially recognized until 1972, Roberta Gibb (Bingay) became the first woman to run and successfully complete the race, finishing in 3:21:40.

1967

New Zealander Dave McKenzie led a record field of 601 starters while setting a course record of 2:15:45. Dartmouth College alumnus Tom Laris finished second with the fastest American time (2:16:48) over the Boston course to date. On the women's side, Roberta Gibb finished first again (unofficial) in 3:27:17. Yet the story of the day focused on Kathrine Switzer, who obtained a number by entering as "K. Switzer." This did not settle well with the race officials and as John "Jock" Semple attempted to remove her number in mid-race, he was cut down by Switzer's burly boyfriend. Pictures of the incident were seen around the world.

1968

Wesleyan University student Ambrose Burfoot gave American runners their first victory in 11 years as the field grew to a record 900 runners. Burfoot, coached by former winner John J. Kelley, finished in 2:22:17 in the warm 72-degree sunshine. Burfoot made his move against U.S. Marine Bill Clark over the final five miles to earn a 38-second victory. Roberta Gibb (unofficial again) was the leading female finisher in 3:30:00. A total of three women finished the race this year. This also marked the final year the race was held on a day other than Monday. The following year, Patriots' Day was designated to be celebrated on the third Monday in April.

1969

The field topped the 1,000 mark for the first time (1,152), which led to the inclusion of qualifying standards at the following year's race. Japan once again raced to the forefront as Yoshiaki Unetani unleashed a superlative effort in taking down Dave McKenzie's course record by nearly two minutes in 2:13:49. Unetani ran alone over the final nine miles as Mexican runners Pablo Garrido (2:17:30) and Alfredo Penaloza (2:19:56) finished second and third, respectively. Three women - running unofficially - finished, led by Sara Mae Berman from Cambridge, Mass. in 3:22:46.

1970

On a rain-soaked, 44-degree day, Englishman Ron Hill devastated Unetani's year-old mark with a stunning 2:10:30 course record. In the process, Georgetown alumnus Eamon O'Reilly lowered the American record to 2:11:22, which was also under Unetani's previous mark of 2:13:49. The entry qualifying time of four hours (or the equivalent at shorter distances) only succeeded in reducing the field to 1,011 starters. Sara Mae Berman was again the first woman winner in 3:05:07.