Rob Bignell has a singular, simple thought when deciding which hikes make the cut in his library of published trail guides: What makes it special?

He has likely built up some sizable calluses finding answers. In his newest Minnesota-related book, “Headin’ to the Cabin: Day Hiking Trails of Northeast Minnesota,” Bignell said he spent about 300 to 400 hours walking trails (or parts of trails) — and driving. “It kept me in shape.”

That’s some serious mileage by any measure given that this was Bignell’s 13th hiking book (He has since published a 14th, on day hikes in Douglas County, Wisconsin). His first guidebook was “Hikes With Tykes,” inspired by outings with his son, Kieran.

Bignell has a system. For “Northeast Minnesota,” he outlined his area of research, with its parks, state and national forests, wildlife management areas and so on. Then he started looking at what others had written about the region and its trails.

“We looked hard at special features,” Bignell said, singling out vistas, flowers, geography or encounters with wildlife. “One thing we wanted to do in the book was make sure that we didn’t say the same thing about the trail.”

Bignell’s passion for hiking took form early. He said his parents owned 750 acres of woodland in Knapp, in western Wisconsin, laced with streams. “Beginning about the time I was 10, when my parents thought I was old enough to wander off, I did wander off and discover all kinds of things.”

Bignell, 49, of Menomonie, Wis., considered suspending his hiking and backpacking when baby Kieran entered his life. Instead, he adjusted. “As long as [Kieran] had the neck strength to hold up his head, we could go hiking. I could hold him on my back,” Bignell said. “He’s lighter than the backpack I was used to carrying. I just had to get used to doing short hikes rather than long backcountry hikes.”

Now 8, Kieran was just 4 months old when his father hiked him into Humboldt Redwoods State Park in northern California. Things like diaper-changing and bottles were dealt with on the fly, but Bignell said he realized his baby boy liked the experience.

Bignell began to research how to hike with children and talked with other parents. The idea for a book struck when Kieran was 3. The two were hiking in Southern California. A bunch of schoolkids were nearby. An adult from the school group noticed Bignell’s child backpack and was wildly interested for his own pursuits. “I started giving the guy tips — like bring a bag to put diapers in and extra diapers. He said, ‘You know a lot about this. You should write a book.’ So I said, ‘Yeah, I think I will write a book,’ ” Bignell recalled, laughing.

His first book, in 2011, set the course for more. “Every year as my son grew older I encountered new problems, and I needed to come up with new solutions to them.”

“Hikes With Tykes: Games and Activities” published a year later.

When his son could walk, there were the limits of keeping hikes to a few miles. Bignell said that changed how he thought about hiking. He started thinking about day hikes rather than backpacking, and his written hiking guides took a different path. Most of his day hikes, on average, are about 2 miles.

Bignell’s initial “Headin’ to the Cabin” book was to focus on northern Wisconsin and Minnesota and Michigan’s Upper Peninsula before he realized it was too broad to tackle well. “I quickly realized after two to three weeks of research that there is no way that you could write about that vast an area in a single book.”

Solution: Divide the “Cabin” books by region. Northwest Wisconsin was the first. He has a third series, too, that focuses tighter still. His “Hittin’ the Trail” books centered, for example, on day hikes in counties or even a park system such as the St. Croix National Scenic Riverway. “Day Hiking Trails of Douglas County” came out in August.

Like the hiking possibilities, his book ideas are plentiful, Bignell said. “I have a list of 150 books to do.”