It would be five more years before women were officially invited to race in the Boston Marathon, but Switzer's actions during the 1967 race are remembered as the trail-blazing effort that propelled women into competitive running alongside men. Rupp, the Olympic bronze medallist in the event, finished second in his first big-city American marathon in 2:09:58 and Suguru Osako of Japan was third in 2:10:28.
In the women's competition, runners to watch include Kenya's Gladys Cherono, who won the 2015 Berlin Marathon, and Edna Kiplagat, who finished second in Chicago past year.
Each year thousands of people swarm to Boston to attend the oldest marathon in the country.
Kathrine Switzer was a few miles into her history-making run at the Boston Marathon on April 19, 1967, when Jock Semple, the co-director of the famous 26-mile race, suddenly appeared behind her and tried to shove her out of the competition.
Kiplagat finished with a time of 2:21:53 seconds in her Boston Marathon debut.
Keflezighi, who plans to retire from racing after the New York City marathon in November, stopped after his victory to touch the hand of Bill Richard, whose 8-year-old son Martin was the youngest person to die in the bombing.
American Jordan Hasay, making her debut at the 26.2-mile distance, was third and Desi Linden was fourth the first time since 1991 that two US women have finished in the top four.
Jordan Hasay from the United States, who was making her debut in marathon clocked 2:23.00 for third place. Desi Linden, who was second in Boston by 2 seconds in 2011, finished fourth - the first time since 1991 that two US women have finished in the top four.More news: Arkansas inmates scheduled for execution ask court to review
Their victories marked a sweet return to the top for Kenya after rival Ethiopia's 2016 sweep behind Lemi Berhanu Hayle and Atsede Baysa.
Also in the men's race, former Ducks Shadrack Biwott was fourth in 2:12.08 and Luke Puskedra, who lives in Eugene, was ninth in 2:14.45.
Marcel Hug won Boston for the third time, outpushing 10-time champion Ernst Van Dyk down Boylston Street and finishing in 1:18:04 to beat the course record and world best by 21 seconds.
The winners' times are considered a world best and not a world record.
"It is humbling to have been chosen to create a work of art that will honor the victims of the 2013 Boston Marathon attack", Eduardo said in a statement.
Pablo Eduardo is a MA resident and internationally known sculptor.
Runners who are blind, wear prostheses or have other challenges set off from Hopkinton, Massachusetts, on Monday morning.
The warm temperatures that hit 79 degrees at the 20-kilometre mark in slowed the runners but the strong tailwind was a boost - especially for the wheelchair races.