By Matthew Huff
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 2023 to 2025. 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. San Francisco Half Marathon
- Where: San Francisco, CA
- Percentage Growth (2023-2025): 131.5%
- Absolute Growth (2023-2025): 4,053
The half marathon that has grown the most in the past three years is the San Francisco Half Marathon Presented by Sutter Health, a 40+ year old event held every February in Golden Gate Park by the Pamakid Runners. For the first time in recent event history, the 2026 race sold out, welcoming more than 9,500 runners (a 30% increase year over year) to compete in the 5K, 10K, and Half Marathon.
The San Francisco Half Marathon’s race director, Michelle La Sala, credits both the strong SF community and iconic route for the influx of runners. “The San Francisco Half Marathon is a very special race and a stronghold in the Bay Area running community,” she says. “Runners continue to show up for this race, both returners and newcomers alike, this year to a complete sellout tune. Running through Golden Gate Park and along the Pacific Ocean with proceeds benefitting the local community, everybody wants to be a part of it.”
Since the event’s inception in 1984, Pamakid Runners have partnered with local nonprofit organizations that support healthy communities and families. Over the past fifteen years, Pamakid Runners has donated more than $1 million back to the Bay Area community. This year’s race beneficiaries included Girls on the Run Bay Area, Running for a Better Oakland, and Support for Families of Children with Disabilities.
2. NYCRUNS Brooklyn Experience Half Marathon
- Where: Brooklyn, NY
- Percentage Growth (2023-2025): 109.5%
- Absolute Growth (2023-2025): 12,855
NYCRUNS Brooklyn Experience Half Marathon is not only one of the fastest growing races in America, it’s now also one of the biggest, earning 3rd place on our list of the most popular half marathons of 2025. The race was only founded in 2011, but quickly drew runners as an alternative to NYRR’s Brooklyn Half. The NYCRUNS marquee race grew from 11,735 finishers in 2023 to nearly 25,000 in 2025.
“Since its first days 16 years ago as a standalone marathon event in Prospect Park with a few hundred runners, the NYCRUNS Brooklyn Experience Half Marathon has grown into New York City’s hottest springtime running event and its only truly authentic Brooklyn running experience, says Steve Lastoe, the Founding CEO of NYCRUNS.
While not included in our data for our 2025 list, Lastoe is quick to point out the success of the 2026 interaction (which we’ll include in next year’s list once all the 2026 races have concluded).
“With a course that showcases the borough’s iconic neighborhoods and majestic waterfront views, the 2026 race featured an event record 28,052 finishers, boosted by tens of thousands cheering supporters,” he says. “75% of the registrants were under 35 years old. The field included entrants from 68 countries, including 49 states, Puerto Rico, and Washington, DC. Two-thirds of the runners were from New York City’s five boroughs, while over 500 charity runners raised funds for 33 nonprofit organizations.”
3. Jersey City Half Marathon
- Where: Jersey City, NJ
- Percentage Growth (2023-2025): 81.9%
- Absolute Growth (2023-2025): 2,190
One of the newest half marathons on this list is the Jersey City Half Marathon, which only launched in 2023 with 2,674 runners. The race was launched in tandem with the Jersey City Marathon several years after the New Jersey Marathon, which ran in Long Beach, was run for the final time in 2019. Post-pandemic, the Jersey City Half became the largest in the state, now boasting nearly 5,000 finishers.
4. Cambridge Half Marathon
- Where: Cambridge, MA
- Percentage Growth (2023-2025): 81.0%
- Absolute Growth (2023-2025): 4,167
Cambridge, Massachusetts’ half marathon had only 5,143 finishers in 2023, and in 2025 that number had grown to 9,310.
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 Charles 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. Boulderthon
- Where: Boulder, CO
- Percentage Growth (2023-2025): 80.0%
- Absolute Growth (2023-2025): 2,359
The Boulderthon’s half marathon nearly doubled in size between 2023 and 2025, with the Colorado half drawing in over 5,300 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. “This year, we’re pledging $50,000 to Tom Watson Park, where many local runners start their long runs on the backroads.”
“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.”
6. The Good Life Halfsy
- Where: Lincoln, NE
- Percentage Growth (2023-2025): 75.5%
- Absolute Growth (2023-2025): 3,788
7. Charlotte Half Marathon
- Where: Charlotte, NC
- Percentage Growth (2023-2025): 56.5%
- Absolute Growth (2023-2025): 1,627
8. La Jolla Half Marathon
- Where: San Diego, CA
- Percentage Growth (2023-2025): 55.8%
- Absolute Growth (2023-2025): 1,596
9. Life Time Chicago Spring Half Marathon
- Where: Chicago, IL
- Percentage Growth (2023-2025): 52.0%
- Absolute Growth (2023-2025): 2,496
10. Santa Barbara Half Marathon
- Where: Santa Barbara, CA
- Percentage Growth (2023-2025): 50.5%
- Absolute Growth (2023-2025): 1,498
11. Eugene Half Marathon
- Where: Eugene, OR
- Percentage Growth (2023-2025): 50.2%
- Absolute Growth (2023-2025): 1,554
12. Long Beach Half Marathon
- Where: Long Beach, CA
- Percentage Growth (2023-2025): 49.6%
- Absolute Growth (2023-2025): 4,036
13. Bank of America Chicago 13.1
- Where: Chicago, IL
- Percentage Growth (2023-2025): 46.3%
- Absolute Growth (2023-2025): 3,023
14. Marine Corps Historic Half Marathon
- Where: Fredericksburg, VA
- Percentage Growth (2023-2025): 45.5%
- Absolute Growth (2023-2025): 1,380
15. Cleveland Half Marathon
- Where: Cleveland, OH
- Percentage Growth (2023-2025): 43.0%
- Absolute Growth (2023-2025): 1,216
16. Oklahoma City Memorial Half Marathon
- Where: Oklahoma City, OK
- Percentage Growth (2023-2025): 38.7%
- Absolute Growth (2023-2025): 2,465
17. Portland Half Marathon
- Where: Portland, OR
- Percentage Growth (2023-2025): 33.3%
- Absolute Growth (2023-2025): 1,259
18. Love Run Philadelphia Half Marathon
- Where: Philadelphia, PA
- Percentage Growth (2023-2025): 33.0%
- Absolute Growth (2023-2025): 1,892
19. Thanksgiving Day Half Marathon
- Where: Athens, GA
- Percentage Growth (2023-2025): 32.0%
- Absolute Growth (2023-2025): 1,520
20. Ascension Seton Austin Half Marathon
- Where: Austin, TX
- Percentage Growth (2023-2025): 32.0%
- Absolute Growth (2023-2025): 2,647
21. Columbus Half Marathon
- Where: Columbus, OH
- Percentage Growth (2023-2025): 30.8%
- Absolute Growth (2023-2025): 2,113
22. Monterey Bay Half Marathon
- Where: Monterey, CA
- Percentage Growth (2023-2025): 29.0%
- Absolute Growth (2023-2025): 1,554
23. Detroit Free Press International Half Marathon
- Where: Detroit, MI
- Percentage Growth (2023-2025): 26.6%
- Absolute Growth (2023-2025): 2,373
24. San Diego Rock ‘n’ Roll Half Marathon
- Where: San Diego, CA
- Percentage Growth (2023-2025): 23.7%
- Absolute Growth (2023-2025): 3,333
25. 500 Festival Mini Marathon
- Where: Indianapolis, IN
- Percentage Growth (2023-2025): 23.6%
- Absolute Growth (2023-2025): 3,359
