DENVER– It was perfect running weather Sunday morning as thousands of people participated in the Colfax marathon that kicked off at 6 a.m. in City Park.

Denver’s only marathon started 13 years ago and has continued to grow, attracting runners from out of state and even out of the country.

20,000 people over the course of 2 days ran the full marathon in addition to 3 other races.

Friends and family stood along the course cheering on the runners.

“Conditions, atmosphere were amazing. I couldn’t ask for better temperature and people on the course that were cheering  as we were digging through it,” said Scott Dahlberg, men’s Colfax Marathon winner.

It’s an incredible growth for the marathon in the last 13 years, starting with only 4,000 runners back in 2005.

“We have people from 47 different states as well as a number of different countries,” said Andrea Dowdy, Colfax Marathon CEO.

Scott Dahlberg was the first to cross the finish line Sunday morning, his first ever marathon.

“Well it was my first marathon I’ve ever done ,so I guess it was a personal record!” said Dahlberg.

Most of the course goes up Colfax but runners also cruised through parts of downtown throughout the morning as well.

“All these great features, we can really show the rest of the world when these people come to run the race, so it’s been terrific,” said Dowdy.

About 40 percent of today’s participants ran for charities, raising about a half million dollars total.