Runners never forget crossing the finish line at their first marathon, and that will be especially true for Detroit Lakes, Minn., native Mike Kohler.

When Kohler crossed the starting line in Fargo last Saturday, he thought he was going to run 13.1 miles, his first half marathon. Six hours later, he had “mistakenly” completed his first full marathon, 26.2 miles.

Kohler, a 26-year-old plumber who now lives in West Fargo, had lined up for the half marathon, earbuds firmly in place to pipe in the soundtrack for the journey that he hoped to complete in two hours and 30 minutes. He didn’t realize he was in a starting corral with the full marathoners. “I heard them say something about half marathon runners but that was it. I didn’t think anything of it,” Kohler said.

Several miles later, Kohler began to realize he was on the course for the full marathon. “The 8-mile mark is when I figured out that I had made a mistake,” he said. “Between then and 13.1, I debated with myself about what I should do.”

At some point — he doesn’t remember when — he doubled down on the distance. “After I decided I was going to keep going, the thought of quitting didn’t come back. Run, walk, or crawl, I wanted to finish,” he said.

He kept going with the upbeat songs and defiant lyrics, including “Not Afraid,” by Eminem, “Bring Me Down,” by Pillar and “Shake It Off,” by Taylor Swift.

At the finish, Kohler didn’t complain when race organizers gave him the medal for a half-marathon finisher. “I just took whatever medal they gave me. I was too tired at the time and didn’t want to explain what happened.”

Until Saturday, Kohler’s longest race was a 10-kilometer run, just over 6 miles. He’d also done some 5Ks, an 8K and an obstacle run.

His longest training run was just over 10 miles. Even the most casual marathoners do a training run of 18 miles before the race. Kohler wasn’t sure, but said he thinks he ran about 10-20 miles a week before the Fargo contest.

From his experience, he said he learned two things: Only have one earbud in at the beginning of the race. And sometimes people can do way more than they think they can.

Kohler had been an athlete. The 2009 Detroit Lakes High School graduate was a defensive lineman a year behind Minnesota Vikings’ scrappy wide receiver Adam Thielen.

The newly minted marathoner already has the grit of a veteran. After his long race, he went right back to work, put in a 10-hour day, then boarded a flight to Scotland for a vacation.

“I was pretty sore, but I found the more I kept moving the less sore I was, so I tried my best to go about life normally — minus running,” Kohler said from Glasgow. “I needed a break from that for a bit.”

Not for too long, though. He’s already considering the Bemidji Blue Ox Marathon in October.