Since the bombing at the 2013 Boston Marathon, the event has come to represent the city's resilience. What's changed in the wake of more recent terror attacks in Paris, Brussels and San Bernardino?
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The 120th Boston Marathon will be held tomorrow, three years after bombs exploded near the finish line. From Boston, NPR's Arun Rath gives us a preview. And he also takes a look at the shadow still cast over the event by the 2013 attack.
ARUN RATH, BYLINE: The best place to follow the Boston Marathon in obsessive, granular detail is in a Cold War era underground bunker about 23 miles from the city, but it's not really the best way to enjoy the event.
KURT SCHWARTZ: There are some holidays and some events - I don't enjoy them the way other people do.
RATH: Kurt Schwartz is the director of the Massachusetts Emergency Management Agency. On Monday, he'll be monitoring feeds from thousands of cameras, police reports, reports called in from suspicious citizens, even notices from acoustic sensors listening out for the hum of drones. By the way, if you're planning on coming, please leave your drone at home. The marathon is a drone-free zone. Protecting an entire marathon from start to finish is a logistical nightmare.
SCHWARTZ: You know, this is a difficult event to put together a comprehensive security plan - because it's 26.2 miles, up to a million people. Most areas are wide open, and you can't physically secure them like a stadium.
RATH: Schwartz says the public probably won't notice anything different this year, but authorities have made adjustments based on recent terror attacks in other cities.
SCHWARTZ: We exercise lots of different scenarios, including the methods of attack that we saw in Brussels, twice in Paris and San Bernardino in - you know, in the past year. So when we ask what if that happened here, it means that we have moved resources in different places, we've staged them differently than perhaps we did a year before.
RATH: For obvious reasons, Schwartz won't go into more detail. But you should not get the impression that the city as a whole is obsessed with security. It's not that anyone is forgetting the bombing or wants to forget. It's just that the marathon is such a huge and historic event, and the bombing is now becoming part of that 120-year history.
DAVE MCGILLIVRAY: Now it's part of the DNA of the event for sure.
RATH: Dave McGillivray is the race director of the Boston Marathon and a distinguished runner himself.
MCGILLIVRAY: It just seems that right now, things have sort of come full circle, that there's a new normal. But things are sort of returning to the way they were a little bit.
RATH: McGillivray says he feels a certain serenity around this year's marathon. And there are plenty of symbols of healing since the 2013 bombing, including 32 survivors slated to run this year, among them Adrianne Haslet, a professional dancer who lost a leg in the bombing. She's dancing again. And on Monday, she'll be running the marathon, raising money for a charity for others who have lost limbs.
ADRIANNE HASLET: It means the world to me to be running for Limbs for Life to help other people get the mobility and dream big so they can run or they can dance - they can do anything that they want to do.
BOBBI GIBB: Even more than a racing event, it's a celebration of life and the human spirit.
RATH: That's Bobbi Gibb, who represents another part of Boston Marathon history. Fifty years ago, she was the first woman to run the marathon unsanctioned. It simply wasn't open to women in those days. Gibb hid in the bushes and slipped in among the racers after most of them made their start.
GIBB: Well, it's always wonderful coming back here. I mean, it feels like I'm coming home. And the Boston Athletic Association is sort of my second family, so I feel very comfortable here.
RATH: Some other women are feeling comfortable, too. Fifty years after Gibb jumped out of the bushes in Hopkinton, 14,000 women will be running this year in the Boston Marathon.