Running a marathon is enough of a challenge for a lot of people, but one man from New York City has made it his mission to run a marathon in all 59 U.S. national parks, on courses that he maps out himself.

Impressively, Bill Sycalik is more than two-thirds of the way done with completing what he calls a “life-experience project.”

Most recently, he’s raced with his friend Ron Peck at Rocky Mountain National Park, the day before Colorado’s most recent (yet unseasonably and unfashionably late) snowstorm. That was the 42nd national park he’s raced across, and Colorado's other three parks await his tread.

If (or really at this point, when) Sycalik reaches his goal, he’ll have run 1545.8 miles. So far, he’s run 1100.4 miles.

Sycalik is not running an organized race or marathon, as most national parks wouldn’t allow something so commercialized.

“Because the park is for the people,” he said. “It’s not for commercial gain.”

What he does is design a 26.2 mile course with the help of a topographical map and park rangers’ assistance, wait for a beautiful day and takes his “joy run” through the park.

And how does one settle on such a project?

In December 2015, when he was looking to get out of New York City. He was unhappy in his job as a management consultant, and the city had lost its luster and exciting newness. He felt cut off from nature and the trails he enjoyed.

“It wasn’t feeding me anymore,” he said. “It was really feeding on me.”

He wanted to get out, take time off and find a place close to nature where he could plant his roots. But he didn’t know what to do with his time off. Then, Sycalik read about the National Park Service’s 100th anniversary, and he decided to marry his love of trail-running with visits to all the national parks as his time-off project.

Yet, not even that was enough. He had to go one step further.

“Just sort of thinking it through to myself, I thought, ‘Why don’t I make it hard?’” he said.

So in June 2016, Bill started running personal marathons in national parks, beginning with Acadia.

It’s definitely not easy. There comes a point about a mile into every single run where he feels tired, as you do after running a mile in nature. He combats this by trying to get in touch with a more animalistic side. Running is different from hiking, requiring more focus and ability to live in the moment rather than stopping to appreciate your surroundings.

“You’re part of nature,” he said. “You’re actually part of the surroundings, as we had been for thousands of years, but we’ve forgotten about it. And it gets you connected to that again.”

Sycalik says it’s also better for the body than running on a flat track, as the uneven surfaces give the body more of a workout. He also finds the outdoors naturally more stimulating than watching the suburbs as you run on the street or the wall by a treadmill as you run without going anywhere.

“It gives you an energy that you don’t get running in a gym,” he said.

People who don’t run treat what he’s done as an impressive accomplishment, but he argues that everyone has it in them to run a marathon. From there, they could run a marathon a week, and then they could do so over natural terrain.

Photos: Marathon through Rocky Mountain National Park

"I believe people can do it,” he said. "It’s whether they want to or not.”

Still, if you’re not a runner but want to change, don’t go straight for running all 59 national parks. Find a coach, to help you know what it is you’re doing. Start slow, as doing otherwise may turn you off the endeavor, he said.

He didn’t get to where he is now overnight. He started running at 33, never having done it before in high school or college.

“When I first started running, it was terrible,” he said.

He didn’t enjoy it for a long time, staying at it because he wanted to get in better shape. Now he’s 45 and running national parks.

When he started his quest, Sycalik only had a stereotypical image of what a national park was like in his mind, which was that they were all something like Rocky Mountain National Park. Instead, he's found a "huge variety" in what he's seen, from desert, rock sculptures and wetlands to the expected mountains.

Colorado’s parks are great example of national park diversity, he said. From the mountainous and the canyon-filled, to the historical and the strange.

He's also encountered the expected wildlife: deer, elk, bison and bears. His first literal run-in with a bear had the creature fleeing from him as he ran, frightened off by the sound of his running.

"I think we were both surprised," he said.

Along with the other three national parks in Colorado, Sycalik still has to run eight in Alaska, two in Hawaii, Grand Canyon National Park, Sequoia National Park, Kings Canyon National Park and the National Park of American Samoa. He estimates that he can finish all but the ones in Alaska this year. He'll have to wait until next year to finish those, as it would be getting too late in the summer to run Alaska if he tried to complete them all now.

After Sycalik runs all the national parks and finishes his project, his goal is to settle into the Denver area, as he has some friends here. From there, he wants to work in an industry he’s passionate about, such as vegan nutrition or outdoor clothing, footwear and accessories.

He’s also interested in the idea of public speaking, in talking about staying open to possibilities.

“When I left New York City, I never thought that I would ever do anything like this,” he said. “I never thought that I would break out of that typical corporate lifestyle.”

But he found he didn’t have to do what was expected of him, and he wants to inspire others to similarly break away. A big change is possible if it’s planned for, he said.

For further updates on Sycalik's journey, or to see some of the highlights and photos from his past runs, check out his Youtube, Instagram and Twitter. Or look at his website