13.1-mile distance saw record growth in 2012.
Half-marathons are the most popular races in the United States, according to the RunningUSA Annual Half-Marathon report.
There were about 1.85 million finishers in half-marathons last year, a new record. The figure was a 14.9 percent increase from 2011, up from 1.61 million.
In 1,136 13.1-mile races, there was a 5.1 percent increase in finishers from 2011 to 2012. The number of finishers in U.S. half-marathons has risen by at least 10 percent every year since 2006.
Other factoids about the race distance: 60 percent of half-marathon finishers in 2012 were women; a record 36 half-marathons had 10,000 or more finishers; and there were more than 30 new half-marathons contested.
For more: RunningUSA