It's part of a series of running events that are held across the United States featuring live music throughout the course and a tribute to the U.S. military.
At the same time, sadly, the fear is that these events are a tempting opportunity for terrorists, after the Boston Marathon bombings in April.
An estimated 20,000 people participated in Seattle's first major running race since the attack, and while most runners do it to achieve a personal goal or just for fun, many here are running with Boston in their hearts.
The runners started at Seattle Center, headed south, winding through Seward Park then across I-90 and Lake Washington to Mercer Island and back to Seattle.
It's a grueling endeavor that demands nearly all of one's physical and mental energy.
Yet many of these runners have made room in their thoughts for others, wearing wrist bands in memory of the 260 injured and three killed at the Boston Marathon.
The running culture is about supporting one another---helping a friend or stranger endure pain that can seem to much to bear.
"That was such a sad thing and I was totally, like, I love running and I just remember those people and this is for them," runner Raquel De Hoyos said.
Bomb sniffing dogs served as a reminder: it's important to do more than just remember.
Police made sure they were visible as a deterrent. Undercover officers and FBI agents were also part of the security plan.
"Definitely makes you feel safer and everybody is definitely taking precautions," participant Lori Magaro said.
At the finish line one runner in particular captured the spirit this event.
Steven Martin, running on high-tech prosthetics, is a military veteran who lost both legs in an explosion while serving in Afghanistan.
"I've been back to Boston twice to visit with people who were wounded in the race," Martin said.
The races in Seattle and across the country will go on despite the threat of those who would do us harm.
"What it means is nobody's gonna stop us," Martin said.
Seattle Police reported no serious problems at Saturday's event.
Officers said they appreciated how helpful the public was in pointing out anything that seemed even a little suspicious.
Yon Yilma, 24, who grew up in Edmonds, won the full marathon in 2 hours, 29 minutes, 53 seconds and beat out defending champion Teshome Kekobe.
This was Yilma's first time running the race.
"I just knew as soon as I broke away I had to make a move and maintain my pace," said Yilma, who coaches for the charity training group Team-in-Training. "I love the Rock 'n' Roll marathon - when you're tired the bands really help you out. It feels amazing. It's a lot of work and I've been waiting for this moment for a long time."
Nuta Olaru, 42, of Boulder, Colo. won the women's full marathon in 2:52.40.
Pat Rizzo of Boulder won the men's half-marathon in 1:05;58.
Nikki Gamble Leith, 29, Edmonds, won the women's half-marathon in 1:25:08.