A lot of the event's participants plan on hitting the pavement in memory of the three lives lost, as well as the countless others injured, in the Boston Marathon bombings.
James Whiteside of Arlington is one of those runners.
"It just tugs at you so many different ways, because it seems so surreal," Whiteside said.
Whiteside crossed the Boston Marathon finish line, beating the explosions by about an hour. He's laced up for more than 75 marathons and never has he witnessed tragedy on a race course until now.
Peter Accomando is also preparing to run in Sunday's race, but he is thinking about Boston.
"I had two brothers running the Boston Marathon on Monday, and my parents were in the city to watch," Accomando said.
Whiteside added, "I still haven't been able to finalize that emotion to say how I really feel other than sadness for the families."
Whiteside plans to use the George Washington Parkway Classic as an emotional release.
More than 7,500 people will take off in Alexandria for the race.
"I think this is a great race," Whiteside continued. "...I think it would be a travesty if people did not come out, because I think the best way to get over things is to overcome them and to face your fears."
Race organizers met with an array of law enforcement agencies Wednesday to make the course as safe as possible.
"Our first concern is safety and making sure everyone feels safe and comfortable coming to the race," added Pacers Events Managing Partner Kathy Dalby.
Most of the heightened safety plans are being kept under wraps for security reasons. But runners should be aware, they can only carry race issued bags that will be extensively screened.
""[We] will have to do some sweeps of the buses," Dalby explained. "Our bag claim process is going to take a little bit longer, because we will have security there."
There will also be ribbons handed out and a moment of silence honoring the victims in Boston.
Runners in the D.C. area are committed to putting their best foot forward in light of the terrible tragedy.
"There's a spirit about us. Anyone who's run a marathon or run a distance event really understands what that spirit is, and they want to be a part of it," Dalby said. "...we're resilient."
Not a single person has emailed race organizers to request a refund. Races don't typically offer them, and it looks like most everyone who's signed up is still planing to crossing the finish line.
And while the Marine Corps Marathon is six months off, its organizers are already responding to Monday's bombings.
Marine Corps Marathon Organizer Rick Nealis said, "For the next six months, we are going to be really tweaking our plan. We are going to make it even more secure."
Cancellation of the marathon isn't an option, which Accomando understands. He is committed to running in the George Washington Parkway Classic. He considers anything else a surrender to fear.
"This sport is about the triumph of human spirit," Accomando said. "Anyone who is a victim or their families would want runners to keep going, keep running."