Running is having a moment. More and more marathons are selling out each year, Strava is basically the hottest social media app, and our TikTok feeds are full of singles running clubs. Half marathons in particular have gone from an extremely niche hobby to a global phenomenon over the last 25 years.
Now, almost every major city hosts at least one half and many are growing – and fast. Races that were originally run by only a handful of people are now so large that waitlists and lotteries are needed to curb entry sizes. In the past few years some races have gone so far as to double their number of finishers.
At Half Marathon Guide, we’ve been crunching the numbers behind what the fastest-growing major half marathons in the U.S. are according to finishers from 2022 to 2024. Moreover, we’ve been chatting with race directors across the country to find out how the organizers are drawing in more runners.
Here are the 25 fastest growing half marathons in the United States, and some insight from the people who planned them.
1. Bank of America Chicago 13.1
- Where: Chicago, IL
- Percentage Growth (2022-2024): 112.84%
- Absolute Growth (2022-2024): 4,202 Finishers
It’s no surprise that the Bank of America Chicago 13.1 is at the top of this list with a growth rate of nearly 113%. Organized by the same team that’s put on the Chicago Marathon for years, the city’s premiere half only launched in 2022 – but became an instant success.
Executive Race Director Carey Pinkowski attributes some of the half marathon’s popularity to a unique course. “When we launched the Bank of America Chicago 13.1,” he says, “we decided to host the event on Chicago’s West Side. Most of the running events in Chicago take place in the loop or along the lakefront path, so initially people were curious about the course. As word spread, interest grew stronger.”
Since its launch, the race has sold out every year. But the organizers have raised the cap slowly to maintain quality. “We’ve incrementally increased the field size to meet the demand while maintaining an enjoyable race day experience,” Pinkowski says. They don’t want to risk an event that’s too large and unwieldy, especially when relying on word of mouth.
The organizers have also courted interest by including the half within the newly minted Bank of America Chicago Distance Series. Runners who finish the full marathon, the half marathon and the Shamrock Shuffle 8K Run all in the same year earn a special medal – as well as guaranteed entry into the following year’s marathon. As entry into an Abbott World Major becomes increasingly hard to secure, linking your half marathon with the full is a great way to incentivize sign ups.
2. Santa Barbara Half Marathon
- Where: Santa Barbara, CA
- Percentage Growth (2022-2024): 104.74%
- Absolute Growth (2022-2024): 1,945 Finishers
The Santa Barbara Half Marathon also managed to double their number of finishers from 2022 to 2024, upping their totals from just under 2,000 to nearly 4,000. That’s quite the increase, especially given that it’s one of the smallest races on this list.
David Monico, the race’s Event Director attributes the growth to two things: the “general post-COVID boom in running” and FOMO. “We create events for our local communities that ultimately create FOMO for anyone globally to want to be a part of,” he says. “It’s a great flywheel of various components that have led to the growth of our events.”
While some races market themselves heavily to tourists, Monaco says they “want to be really focused on the local community, which has ultimately led to our growth.” To that end, they’ve partnered with local groups like sports teams and colleges to make sure that there’s a strong base of support from the Santa Barbara area.
They’ve also kept their entry fee modest and include special perks for locales who sign up. Through their Artist Program, the Santa Barbara Half Marathon commissions “local artists to create unique one-of-a-kind designs that provide another layer of texture to our events.”
If the Santa Barbara locals are having fun at the half, then others certainly won’t want to miss it either.
3. Boulderthon
- Where: Boulder, CO
- Percentage Growth (2022-2024): 96.84%
- Absolute Growth (2022-2024): 1,811 Finishers
The Boulderthon’s half marathon nearly doubled in size between 2022 and 2024, with the Colorado half drawing in over 3,600 runners last year. Event Director Alexa Squillaro says, “It’s not difficult to promote such a beautiful and iconic location, which many consider the endurance capital of the U.S.” But plenty of races in gorgeous locales aren’t doubling their field size.
Squillaro says that “continuously refining” their strategies with the help of post-race surveys certainly helps to keep improving any weak spots in their event. Some changes that they’ve made recently include reimagining their course by “bringing the start and finish to downtown Boulder to showcase both the vibrant energy of the city and the breathtaking views of the Flatirons.”
They also upgraded the quality of their finisher shirts and medals (which are now 100% recycled) and invested heavily in over 600 volunteers.
“Start with your post-race survey,” Squillaro says, circling back to that key aspect of their strategy. “Collect the insights, analyze the trends, and prioritize investing in your participant experience above all else.”
4. Cambridge Half Marathon
- Where: Cambridge, MA
- Percentage Growth (2022-2024): 84.62%
- Absolute Growth (2022-2024): 3,350 Finishers
Cambridge, Massachusetts’ half marathon had less than 4,000 finishers in 2022, and in 2024 that number had grown to over 7,000.
Leslie Medalie, who handles the race’s public relations says, “One of the major attractions is the Cambridge Half Marathon’s new course.” Starting and finishing at CambridgeSide, a shopping center, “the scenic course runs alongside the Chalres River on Memorial Drive and features views of MIT, John W. Weeks Footbridge, Harvard University, and more.”
Medalie also points out, “It is important to put on a good event with swag that runners are interested in.” Rather than the usual finisher t-shirt, entrants in the Cambridge Half get a quarter zip pullover as well as post-race refreshments.
The race also raised over $400,000 for local nonprofits in 2024 which makes the race a pivotal part of the community in addition to just being fun.
5. The OC Half Marathon
- Where: Costa Mesa, CA
- Percentage Growth (2022-2024): 80.47%
- Absolute Growth (2022-2024): 4,377 Finishers
Rounding out the Top 5 is Orange County’s half marathon, which expanded from only 5,439 finishers in 2022 to nearly 10,000 in 2024.
The OC Half’s Event Marketing Manager Adrienne James says that the running club boom has definitely helped their numbers. “We have a strong relationship with our community,” she says, “From our 120+ run clubs to our 75+ corporate teams and 30+ charity partners. Run clubs specifically have seen huge growth, especially with a younger demographic. We have a robust ambassador program that does a lot of work for us in keeping the community engaged.”
The OC Half is also leaning into social media. “We started an influencer program,” James says, “that has helped us tap into new audiences around the U.S. as well as connect with a younger demographic.”
Ultimately though, James recognizes that it’s the quality of the race that really brings in runners. “The smallest actions build lifelong customer loyalty,” she says. “Our small team of three works hard to reply to every email, accommodate as many requests as we can and always monitor feedback from our runners. When you have advocates who truly want to go out and tell others about your race, that authenticity reaches people in a way that traditional marketing can’t.”
6. Denver Colfax Half Marathon
- Where: Denver, CO
- Percentage Growth (2022-2024): 70.45%
- Absolute Growth (2022-2024): 2,501 Finishers
7. St. Jude Rock ‘n’ Roll DC Half Marathon
- Where: Washington, DC
- Percentage Growth (2022-2024): 69.9%
- Absolute Growth (2022-2024): 5,256 Finishers
8. Charlotte Half Marathon
- Where: Charlotte, NC
- Percentage Growth (2022-2024): 66.15%
- Absolute Growth (2022-2024): 1,581 Finishers
9. Kentucky Derby Festival Mini Marathon
- Where: Louisville, KY
- Percentage Growth (2022-2024): 59.62%
- Absolute Growth (2022-2024): 2,870 Finishers
10. Oklahoma City Memorial Half Marathon
- Where: Oklahoma City, OK
- Percentage Growth (2022-2024): 53.36%
- Absolute Growth (2022-2024): 2,570 Finishers
11. San Diego Rock ‘n’ Roll Half Marathon
- Where: San Diego, CA
- Percentage Growth (2022-2024): 53.31%
- Absolute Growth (2022-2024): 5,556 Finishers
12. NYRR RBC Brooklyn Half Marathon
- Where: Brooklyn, NY
- Percentage Growth (2022-2024): 51.08%
- Absolute Growth (2022-2024): 9,621 Finishers
13. Flying Pig Half Marathon
- Where: Cincinnati, OH
- Percentage Growth (2022-2024): 43%
- Absolute Growth (2022-2024): 3,169 Finishers
14. Detroit Free Press International Half Marathon
- Where: Detroit, MI
- Percentage Growth (2022-2024): 40.30%
- Absolute Growth (2022-2024): 4,303 Finishers
15. The Good Life Halfsy
- Where: Lincoln, NE
- Percentage Growth (2022-2024): 40.25%
- Absolute Growth (2022-2024): 1,549 Finishers
16. Hapalua Hawaii’s Half Marathon
- Where: Honolulu, HI
- Percentage Growth (2022-2024): 40.14%
- Absolute Growth (2022-2024): 1,918 Finishers
17. Monterey Bay Half Marathon
- Where: Monterey, CA
- Percentage Growth (2022-2024): 39.87%
- Absolute Growth (2022-2024): 1,878 Finishers
18. Capital City Half Marathon
- Where: Columbus, OH
- Percentage Growth (2022-2024): 34.89%
- Absolute Growth (2022-2024): 1,320 Finishers
19. Thanksgiving Day Half Marathon
- Where: Athens, GA
- Percentage Growth (2022-2024): 33%
- Absolute Growth (2022-2024): 1,305 Finishers
20. NYCRUNS Brooklyn Experience Half Marathon
- Where: Brooklyn, NY
- Percentage Growth (2022-2024): 32.30%
- Absolute Growth (2022-2024): 5,304 Finishers
21. Eugene Half Marathon
- Where: Eugene, OR
- Percentage Growth (2022-2024): 32.29%
- Absolute Growth (2022-2024): 953 Finishers
22. Life Time Chicago Spring Half Marathon
- Where: Chicago, IL
- Percentage Growth (2022-2024): 32.15%
- Absolute Growth (2022-2024): 1,291 Finishers
23. DICK’s Sporting Goods Pittsburgh Half Marathon
- Where: Pittsburgh, PA
- Percentage Growth (2022-2024): 31.99%
- Absolute Growth (2022-2024): 2,754 Finishers
24. St. Jude Rock ‘n’ Roll Nashville
- Where: Nashville, TN
- Percentage Growth (2022-2024): 31.15%
- Absolute Growth (2022-2024): 2,659 Finishers
25. San Francisco Half Marathon*
- Where: San Francisco, CA
- Percentage Growth (2022, 2023, 2025): 43.16%
- Absolute Growth (2022, 2023, 2025): 1,070 Finishers
*Note: The San Francisco Half Marathons were canceled in 2024 due to weather, so there are not finisher numbers for that race, but we compared the 2022 results to their 2025 results, and they’ve seen solid growth over time.
