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.
A Kenyan won the women's race as well as Edna Kiplagat posted a time of 2:21:52. Rose Chelimo of Bahrain finished second and Americans Jordan Hasay and Desiree Linden took third and fourth. "When Americans break the tape, it's going to be a big deal here".
But Ethiopia has surpassed its East African neighbors on Patriots' Day the past four years, earning its first sweep in 2016.
"After all the marathons I've run, this may be the most important of all", she said. Times, luckily, have changed and women make up a large percentage of marathon runners. Fellow Swiss Manuela Schar shattered the women's mark by more than five minutes, winning in 1:28:17. The straight-line Boston course doesn't qualify for world records because of the possibility of a supportive tailwind like the one on Monday. Boston Police Commissioner William Evans also ran for the first time since the Boston Marathon bombings.
Hug outpushed 10-time victor Ernst Van Dyk of South Africa down Boylston Street to finish in an unofficial time of 1 hour, 18 minutes, 4 seconds. Her two-year training regimen included participating in Woodstock Vermont's Hundred Mile Equestrian Race as its first and ONLY runner.More news: Multi-state search targets suspect in Facebook video murder
Also running on Monday was Ben Beach, who completed the race for an unprecedented 50th time in a row. "Everything was fantastic today".
Security was high along the course, which begins in Hopkinton, Massachusetts, and passes through Boston's suburbs to the finish line, where a pair of ethnic Chechen brothers on April 15, 2013 set off two homemade bombs, killing three people and injuring more than 200.
Briggs then entered himself and Switzer - who registered as K.V. Switzer - in the 1967 Boston Marathon.
"In 2013, I was a spectator just like the three victims and when I saw the 8-year-old. the first thing in my mind was that could have been my daughter", said Keflezighi.
Jimmy Golen has covered the Boston Marathon since 1995.