NYC attack: Should there be stronger regulations for car rentals?
The race has been canceled only once in its 47-year history - in 2012, following Superstorm Sandy's devastating hit to the region. It even went forward after the Sept. 11, 2001, attacks, which killed about 2,600 people in New York.
Marathoners train for months to prepare for the 26.2-mile (42.2 km) race, and some wait years before winning a spot in the drawing that gives about 30 percent of them access to a field that includes the world's top runners and draws about 2.5 million spectators.
"The determination that got them here is the determination that I think that they have right now going into Sunday," Weiller said.
BOSTON MEMORIES
Sunday's race will not be the first time U.S. runners have had to worry about violence. Two brothers inspired by al Qaeda killed three people and injured more than 260 with bombs at the finish line of the 2013 Boston Marathon.
Philadelphian Neil Gottlieb remembers that attack vividly as it occurred shortly after he crossed the finish line. But he was back on that course in 2014 and said he was undaunted from racing in New York.
"I'm not going to win the New York City Marathon, but it's a victory for me, and I'm not going to let anyone stop me," said Gottlieb, a 48-year-old healthcare executive and father of three.
New York police stepped up security, saying they would deploy extra "blocking trucks" to protect against vehicle attacks, rooftop snipers, heavy weapons, dogs and helicopters.
"This increase will supplement the already large, substantial detail of uniformed officers that you will see along the route," New York Police Chief Carlos Gomez said on Wednesday.
In addition, the state Police, National Guard and the Metropolitan Transportation Authority and the Port Authority of New York and New Jersey will increase deployments at airports, bridges, tunnels, and mass transit systems before and after the race, New York Governor Andrew Cuomo said on Saturday.
"While there is no apparent threat, we are ramping up security across New York City with patrols and resources from various state law enforcement agencies out of an abundance of caution," Cuomo said in a statement.
The marathon route connects all five of the city's boroughs, starting near the Verrazano-Narrows Bridge in Staten Island, snaking through Brooklyn, Queens and Manhattan, before circling up to the Bronx and back to Manhattan.
Stephanie Trumbino, 35, of Maplewood, New Jersey, said she felt concerned about the attack but did not consider missing her first attempt at the race.
"I never gave it a second thought," said Trumbino, a human resources manager at Stevens Institute of Technology in Hoboken, New Jersey.
(Reporting by Peter Szekely and Barbara Goldberg in New York, and Chris Kenning in Chicago; Editing by Andrew Hay and Matthew Lewis)