Last month, I noticed that the Philly Marathon and Twin Cities Marathon had both sold out earlier than usual. That got me wondering how widespread of a phenomena this was, and last week I gathered the data on four more marathons: Colorado, Denver, Detroit, and Miami.
As if to illustrate the point that races are starting to sell out more quickly, registration for the 2026 Miami Marathon was still open the day I published that last article … and it was sold out just a few days later. Registration for the race opened on August 1, so it sold out in less than two weeks.
After gathering some more anecdotal evidence from other runners about what races are selling out, I’ve gathered data on five more races: Boulderthon, Columbus, Indy, Dallas, Toronto Waterfront, and Grandma’s. And the trend is shaping up pretty clearly – it’s not just a handful of races. Many races are selling out – and in many cases, it’s happening earlier than in past years.
I’m going to continue to collect some data to help paint the bigger picture, but for today here’s the rundown on these five races.
Boulderthon Marathon
Boulderthon is now the third Colorado race that I’ve looked at – after the Colorado Marathon and the Denver Colfax Marathon. It’s a newer race and it was originally smaller, but it’s grown year over year and it’s shaping up to be one of the most popular races in the state.
In it’s inaugural year (2021), the full marathon had only 389 finishers. The next year, the race had grown to 554 finishers. That year, the half marathon and the 10k sold out – but the full marathon still had bibs available through race week.
The following year (2022), the field size increased to 917 marathon finishers – and many more runners at the other distances. By September 23, the 5k and the 10k sold out. But the half marathon and full marathon remained open for registration.
The race continued to grow in 2024, with 1,327 finishers. An archived version of the website shows that the marathon was sold out on September 18, and an announcement was made on Instagram on September 16. This is the first time the full marathon sold out.
This year (2025) is slated to be bigger and better. The field across all races is expected to increase from 10,000 to 15,000, with about 3,000 finishers in the full marathon. This year’s marathon sold out by the end of July, far earlier than the previous year. That increased velocity is even more notable, given the fact that there are twice as many registrants.
If the race does increase to over 3,000 finishers, it will be climbing the list of the largest races in the United States. That field would have placed it #27 on last year’s list of the largest races, in between the Dallas Marathon and the Eugene Marathon. That’s impressive for a race that just started a few years ago.
Dallas Marathon
The Dallas Marathon is a much older race – dating back to 1971. Recently, it has attracted 3,000 to 4,000 finishers, making it one of the largest races in the country. In the days before COVID, though, I couldn’t find any evidence that this race routinely sold out. The same is true in 2022.
In 2023, the race did sell out. On November 28, they were still advertising registration on Facebook. But by the time the expo rolled around, it was sold out. This was the first year that the entire weekend full of events was sold out.
That sellout occurred just days before the race. But in 2024, the race was full by October 18 – five or six weeks ahead of the race. Registration for the 2025 race is open now, and we’ll soon find out if it fills up earlier than last year.
Columbus Marathon
Columbus is another medium to large race, similar in size to Dallas. Although it’s always been popular, it wasn’t a sell-out race back in 2019. In the days leading up the race, they were still advertising registration.
But since 2022, it has sold out. That year, they announced the sellout on Facebook on September 30.
The next year, 2023, the sellout was announced on Facebook on September 12. But an article in the Columbus Dispatch indicated that the race had sold out the week before, on September 5. The time frame was similar in 2024, with a Facebook announcement on September 11. I couldn’t find a news article with a specific date.
Just a couple of days ago, they announced that the race was on track for an August sell out. Between the larger trend and the fact that this race has sold out in September the last few years, that seems pretty plausible. If Columbus is on your to do list, I’d sign up ASAP – because it could well be sold out in the next week or two.
Indy Monumental
The Indy Monumental Marathon is a relatively new race, compared to the others on this list. It started in 2008. But it grew in popularity pretty quickly.
By 2019, the race did sell out – but it didn’t happen until race week. It was also the first year that the 5k, half marathon, and full marathon all sold out.
In 2022, the race sold out about a week before the race – on October 27. The race that year was on November 4.
The next year, it sold out on October 20. The race was a week earlier, though, so this was still about one week before the race. The 2023 race was earlier than usual, on October 28.
In 2024, the race sold out on October 15. This might seem only a few days earlier, but the race itself was later in the year – November 9. This was the 12th consecutive year that the marathon itself had sold out.
Earlier this month, they announced that the marathon was already 75% sold out – and that it was on pace to fill up faster than ever. This is another one to watch over the next month or so. But I wouldn’t be surprised if this ends up sold out in early to mid September.
Toronto Waterfront Marathon
The same thing is happening across the border in Canada. The Toronto Waterfront is one of the largest races in Canada. With over 6,000 finishers last year, it’s the largest race on this list (so far).
In 2023, the marathon sold out for the first time. Runners were taken by surprise, after years of being able to register at the last minute. A Toronto Star article went into some of the reasons. Besides the general surge in runners, there were also logistical constraints that prevented the field from getting much bigger. The sellout was announced on September 5 – about six weeks before the race.
In 2024, things went even more quickly. They announced that the marathon had sold out on August 19. This was despite the marathon field growing quite a bit to just over 6,000.
This year, things continued to trend in the same direction. On June 24, they announced that the race was already 95% full. By July 16, Canadian Running reported that the race was sold out. This was more than a month earlier than in 2024.
Grandma’s Marathon
The final race on the list for today is Grandma’s Marathon – back south of the border in Duluth. Grandma’s has its own logistical issues that limit its potential growth. The area itself has a much smaller population than a large metro area like Toronto, and the course requires participants to be bussed to the start. Still, it’s one of the largest races in the United States with 7,500 finishers this year.
Way back in 2016, the race did sell out. It sold out on December 31, about six months before the race. At the time, this was the earliest it had ever sold out. But over the next few years, it does not appear that the race sold out at all. In 2017, 2018, and 2019, the registration was still open in the days leading up to the race.
When the race returned after COVID, though, it was selling out once again. In 2022, it sold out on May 22. In 2023, it was much earlier – March 23. And in 2024, the race sold out on January 5. This was only days after the record set back in 2016.
What happened this year? The race was sold out on November 6, just over a month after registration opened (October 1). When registration opens up later this year, I’m sure it will go just as quickly – or maybe even quicker.
Will Races Continue to Sell Out Quickly?
The big picture seems pretty clear – races that never sold out before are starting to sell out, and races that were selling out are doing so much more quickly.
The question, though, is how long this will go on for. This isn’t the first running boom, and the sport has retracted before. Before COVID, peak participation – at least among American races – was around 2014 to 2016. Grandma’s is a good example of a race that did sell out at its peak, then stopped selling out, and is now selling out again.
Since 2022, the number of marathon finishers has continued to increase year over year. Last year, it exceeded that previous peak, and this year is on pace to be even bigger.
If (when) this trend turns around, one of the first indications may be that these same races start to sell out more slowly – or stop selling out at all. If you’re just looking at the number of finishers, then things won’t appear to be on the decline. But if it takes longer to fill up some of these races, it’ll be a sign that interest has begun to plateau.
I think this is something worth tracking going forward to maintain a sense of how things are changing. I’m going to run down the list of the largest races from last year and try to organize this data into something more structured.