Kirui outran Galen Rupp of the take the men's race in an official time of 2 hours, 9 minutes, 37 seconds. By 1972, women were "officially" allowed to register for the Boston Marathon (though the nine women who met the strict men's qualifying times were required to run separately from the men).

"I always think that was a 20-year-old girl who simply wanted to run, and somebody tried to stop her and scared her, embarrassed her but also inspired her and propelled her to change her life and to create opportunities for other women", Switzer told NESN this week. As runners from the men's and women's races came down Boylston in droves, the crowd relented and resorted to nonstop cheering. Unfortunately, making the decision to run a marathon wasn't always so simple for women.

It was Evan's 19th time completing the race and his 52nd overall marathon.

Sanchez is running this year's race as part of Team Semper Fi, and is fundraising for the Semper Fi Fund, which is dedicated to providing "immediate financial assistance and lifetime support to post-9/11 wounded, critically ill and injured members of all branches of the U.S. Armed Forces, and their families". Multiple checkpoints are being used as people get closer to the finish line.

Though she finished the race and is a known advocate for women's running today, Switzer's participation in the 1967 marathon wasn't exactly celebrated by everyone.

A strong tailwind and cooler temperatures in 2011 helped Geoffrey Mutai finish in 2 hours, 3 minutes, 2 seconds.

Kathrine Switzer was told that running a marathon was impossible. According to Running USA's 2016 State of the Sport report, females accounted for 9.7 million road race finishers nationwide past year, and represented 57 percent of race event fields.

Atsede Baysa of Ethiopia is back to defend her women's title. Linden took home silver in 2011 and made it clear that she was in Boston hoping to be first across the line and be the first USA woman to do so since 1985. Soon after, Buzunesh Deba who went into the marathon looking for her tenth win on US soil, dropped back from the main group.

The 121st running of the Boston Marathon is getting underway in waves for the 30,000 athletes.

There are three more waves that set up a staggered start: wave two at 10:25 a.m., wave three at 10:50 a.m. and wave four at 11:15 a.m.

The rest of the field will follow in waves.