Sue Johnston poses with her husband, Chris Scott, on Mount Isolation after hiking each of New Hampshire’s 4,000-foot mountains in each month of 2016. Courtesy

Sue Johnston poses in the White Mountains in December. She hiked each of New Hampshire’s 4,000-foot mountains in each month of 2016, becoming the first known person to do so. Courtesy

A New Hampshire woman has become the first known person to complete a vaunted White Mountains hiking challenge – which takes some hikers a lifetime – within a single year.

Sue Johnston of Littleton hiked each of the state’s 4,000-foot mountains in January, and then again in February, and in March, and so on, for a total of 576 peaks in 2016 – plus some extracurriculars.

The quest to hike all 48 Granite State mountains on “The List” in each calendar month is called “The Grid.” Only 70 people have finished it, including Johnston in 2003, when she became the first woman and third overall.

By hiking The Grid in a single year, she has created a new bar for hikers who take on increasingly difficult challenges in the White Mountains.

Johnston, a 51-year-old who previously lived in Danville, Vt., adds the accomplishment to a hiking and running résumé that includes 26 100-mile races, more than a dozen long trails hiked end-to-end and very nearly the high points in all 50 states.

But she said her motivation is more about enjoying time outside than setting records.

“It’s kind of impossible to be in a bad mood while you’re hiking,” she said. “At the beginning, you’re thinking, ‘How am I going to get through? How am I going to finish?’ And then you just do it, and you love every day, or almost every day.”

Her most difficult month, December, when she hiked on 21 days, consistently handed her ugly conditions that made her want to stay below treeline, she said. The skies cleared enough on the 20th and 23rd that she was able to tackle first mounts Monroe to Madison, then Franconia Ridge.

With only three peaks remaining, she finished atop Mount Isolation on Dec. 26.

In July, she hiked a mere 119 hours over 10 days, even while giving herself the additional challenge of walking from mountain to mountain. This most-direct-route style, termed Direttissima, took her from Mount Cabot to Mount Moosilauke, returning to her bed at the end of every day after her husband, Chris Scott, picked her up in their Subaru.

The fact that she could always return home – meaning her pack weight was never too high and she was never too far from good food – made this effort easier than her 1994 thru-hike of the Appalachian Trail, she said.

“I’m really picky about when I go above treeline, because I don’t like strong winds and really, really cold temps,” she said. “If I woke up and the weather was horrible, I just wouldn’t go that day.”

She first had the idea to attempt this feat three years ago after she read on an online forum for hikers someone asking whether it’d be possible. Most people said no, she recalled.

“I said I think you could, if you didn’t work, if you didn’t have kids at home, and I started thinking, ‘That’s me. I have that lifestyle and I love to hike,’ ” she said.

The near requirement to be retired – as she and her husband are – while also maintaining the fitness level to hike so often may be the most difficult aspect of the challenge, she said.

That and the good fortune it takes.

“Nothing bad can happen to you,” she said, noting that she hiked on seemingly nothing but ice for the first few months of the year. “You can’t get sick for more than a few days, you can’t get injured, there’s always family stuff that can come up. Just stuff happens.”

It wasn’t until April that she felt confident she’d finish, she said. At that point, she still hadn’t announced what she was attempting.

For anyone who wishes to push their limits with some athletic challenge, Johnston said first “you have to really love what you’re doing” and then “do your homework, basically.”

It was an advantage for her to know the White Mountains so well – from 30 years hiking there – before she began, she said.

“I’m not saying nothing bad could ever happen to me – because anybody can break a leg, right? – but I know the trails so well, I know the bailout routes, I know in the winter what trail is going to be broken and what isn’t,” she said.

Now that her year of strenuous hiking – and equally meticulous record-keeping – is over, she’s handing 2017 over to her husband, probably to do a little more traveling. She emphasized Scott’s “instrumental” role in driving, cooking, hiking and generally supporting her along the way.

“I kind of told him this year we’d do whatever he wants to do,” she said, adding with a laugh, “He hasn’t given me a detailed itinerary.”

(Nick Reid can be reached at 369-3325, nreid@cmonitor.com or on Twitter at @NickBReid.)