Already a silver medalist and USA record-holder in the 10,000 meters, he ran the fastest marathon time ever for an American in the Summer Games: 2 hours, 10 minutes, 5 seconds.
Keflezighi, whose emotional victory the year after the finish line bombings was the first for an American man in three decades, says he is running Boston for the last time.
Switzer had no intentions of dropping out of that fateful race, nor did she expect to be such a barrier-breaker (Roberta Bingay Gibb had actually completed the Boston Marathon the year before without an official bib).
Marcel Hug won Boston for the third time, outpushing 10-time champion Ernst Van Dyk and finishing in 1:18:04 to beat the course record and world best by 21 seconds.
American Jordan Hasay set a record for an American women's debut marathon, coming in third in 2:23:00.
Olympian Desi Linden surged to finish fourth overall in 2:25:06.
Kirui, 24, produced a devastating sprint with four miles to go to settle an enthralling tactical battle with American rival Galen Rupp, the 2016 Olympic bronze medallist.April 17, 2017; Boston, MA, USA; Geoffrey Kirui and Galen Rupp race in the 2017 Boston Marathon.More news: United to pay compensation to plane passengers
Galen Rupp, 2012 Olympic silver medalist for 10,000 meters and 2016 Olympic bronze medalist for the marathon, is among the contenders, and probably the top US threat in the men's race.
"It's the only marathon in the entire world where you have to qualify, and according to the Boston Athletic Association, they only take the world's top 1% of runners".
Rupp finished unofficially in 2:09.58.
"It wasn't until Jock attacked me that everything changed", she said. As she wrote on her website, a race official tried to stop her out of concern that the distance was too long for "fragile" women to run. He'll create the memorial markers on Boylston Street where bombs killed three spectators and wounded more than 260 others.
The race also marked the return of a marathon legend. Evans, who completed his 52nd marathon overall, said he wanted to show that Boston is back to normal.
A strong tailwind and cooler temperatures in 2011 helped Geoffrey Mutai finish in 2 hours, 3 minutes, 2 seconds.
The elite women are on their way in the 121st running of the Boston Marathon.