In 2010, Mark Baumer, a Rhode Island-based author, poet and activist, set out to walk across America — one foot in front of the other, all the way from the East Coast to the beaches of Los Angeles.

Motivated by a sense of adventure and the challenge of completing the daunting 2,500-mile trip, he hoped to reach the Pacific Ocean within three months. In the end, he took just 81 days.

Baumer, an avid social media user, chronicled the journey in photos and blog posts, and later wrote about it in a memoir he called “I am a Road.”

“I have let America climb on my back,” he said in his final post, “and then I walked across her.”

Six years later, Baumer, 33, decided to do it again — this time completely barefoot and with as few possessions as possible. This time, he would also walk for a cause: raising awareness about climate change.

“I’m sure a lot of people don’t think I can make it across America barefoot and probably even more doubt I will be able to defeat climate change with this journey,” he wrote in September. “But something deep inside of me is telling me to do this so I will do my best to listen to this voice inside of me and ignore all the voices outside of me who don’t believe in me.”

In October, a shoeless Baumer left his house in Providence, R.I. He made it as far as Ohio before harsh winter weather held him up. From there, he took a bus due south to Florida to start fresh in warmer temperatures.

That was where his journey ended.

On Saturday afternoon, just after marking his one hundredth day on the road, Baumer was walking along the shoulder of Highway 90 in Walton County, Fla., when police say an SUV veered out of its lane and struck him. He died at the scene. Police said the investigation is ongoing.

As he did during his 2010 trip, Baumer had been posting about his travels on a blog called Barefoot Across America, as well as on YouTube and Instagram. His last entry featured a photo of him standing above the word “killed” in yellow spraypaint on the asphalt.

“When I began walking I had an urge to stop traffic until all the roads in america died,” Baumer wrote. “One day everyone will be able to walk down the middle of the road free from all the violence this society has built.”

Baumer’s travels — along with his prolific writing, zany performance art and warm, caring spirit — gave him an almost folk hero image among those who knew him and followed his work.

Friends and family described him as highly original, intensely creative and always on the move.

“He was so active, even if you weren’t regularly in touch with him, you’d be constantly watching him do things,” Baumer’s friend Blake Butler told The Washington Post. “I think he hated mundane reality and would do anything he could to inject some awe or joy or unique emotion into life that other people would idly let pass by.”

Baumer went to Wheaton College in Massachusetts as an undergrad and was later accepted into a highly selective MFA program at Brown University. Before he died, he was working as a Web specialist at the Brown library. He had published numerous books, poems and other material, and had won awards for his work, including a poetry fellowship through the Rhode Island State Council on the Arts.

A constant stream of ideas — some of them brilliant, some harebrained — seemed to pour from Baumer, friends said. On one occasion, Butler said, Baumer created a Kickstarter trying to bring in $50,000 to write 50 books in one year. The fundraiser attracted less than $2,000, but Baumer pressed on — and he did, indeed, write all 50 books in 2012. Titles included “The Trauma of Eating a Celebrity,” “The Guy with Two Crossbows,” and, in what was perhaps a jab at himself, “The Books Keep Getting Worse and Worse.”

A penchant for absurd humor ran through much of Baumer’s work, his friend and fellow author Claire Donato told The Post. It was on display, she said, in everything from his writings to his YouTube channel, which features hundreds of stream-of-consciousness videos and eccentric skits.

Donato, who met Baumer through the program at Brown, recalled a reading they did together in Providence over the summer, when Baumer was promoting his book “Holiday Meat,” a work of fiction that won the 2015 Quarterly West novella contest. Rather than read excerpts from one copy, Donato said, Baumer brought ten or 15 different copies to the front of the room and kept swapping them, reading from each.

“It was absurd in the best way,” she said.

But beneath the humor, Baumer was sincere and generous, friends recalled. He ate a vegan diet and didn’t drink or use drugs. He was a frequent meditator and yogi, and stood a towering 6-foot-3. Despite his size and outlandish personality online, he was often reserved and soft-spoken in person, acutely aware of other people’s feelings, friends said.

Baumer was born in Hammond, Ind., and his family relocated to Durham, Maine, when he was a boy. Growing up, Baumer excelled at baseball, and went on to become a star hitter and first baseman for the Wheaton College team, according to his father, Jim Baumer.

Jim Baumer described his son, an only child, as disciplined, introspective and thoughtful. The elder Baumer, a freelance writer, said his son would always comfort him when he became discouraged with his work, saying “Just keep doing what you’re doing, Dad.”

“If we were only going to have one son,” Jim Baumer said, “we couldn’t have done better than Mark.”

The first time Baumer decided to walk from coast to coast, his parents worried.

“He comes home and he just goes, ‘I’m going to do something this summer that I’ve never done before,'” his father said. “It’s not like you’re going to say, ‘No, you can’t do something you set your mind to,’ but there was always this sense that potentially something could happen.”

As he made his way, Baumer’s parents followed his blog closely. At one point, they even flew to Texas and walked 15 miles with him, his father said, marveling at how his son was able to average twice that distance daily.

He started out jogging, but slowed when his feet began to swell. By November, he wrote on his blog, he was trudging through snow and freezing rain. At one point, he spent an entire day in a motel room because, he said, “my feet didn’t work.”

In mid-December, a full two months into his journey, the cold became too much. He took a bus from Ohio to Jacksonville, Fla., to start over.

By his hundredth day on the road, he had reached the Florida panhandle. Donald Trump had just been inaugurated president, and Baumer was distraught.

“We now have a president who does not care about the future of humanity on planet earth,” he wrote.

At some point, his father called him, and the two discussed the future of the country under an administration they both opposed.

“We talked about trying to find hope in a system where the only safety net will be wealth,” Baumer wrote. “Part of me wanted to curl up and wait for my brain to melt but instead I began walking in the rain.”

It would be his last missive from the road.

Donato, Baumer’s friend from Brown, remembered her reaction when she found out he was making a second trek across America.

“My friend is a superhero,” Donato recalled thinking.

“I really believed that,” she continued. “I wanted to believe and still believe even though he’s no longer with us that he’s invincible. I had no doubt in my mind that he could do it.”