Friends to walk the Appalachian Trail
Tom, 21, from Mannamead, and Colin, 19, from Oreston, flew out to Atlanta on Tuesday and were due to set off within a day or two after arrival.
They aim to finish their epic hike by mid-October, after which heavy snow is likely to make trekking in the mountains impossible.
The pair hope to raise up to £15,000 for Cancer Research, and have a special reason for supporting the charity.
Colin's father, Keith Ross, died of prostate cancer aged 54 last October.
Tom, a chef-barman and Colin, a carpenter, expect to cover 15 miles a day, carrying packs of up to 40lb.
They hope to re-supply at small towns once a week, but will have to source water from local streams as they go along.
Tom admitted carrying enough food could be a problem, as they will burn around 7,500 calories a day yomping in the rugged terrain.
But far more dangerous than going hungry could be the wildlife, including black bears, cougars, snakes and parasites.
Tom said: "We will be carrying a mobile phone but not relying on it for rescue if anything goes wrong."
The pair are self-funded and have spent £1,500 each on equipment, with the whole trip expected to cost each of them around £5,000.
Despite sleeping under canvas, they will have help from new technology, taking ipods with solar chargers and carbon-fibre hiking poles.
They also hope to encounter hillbilly internet cafes where they can update their website, and bars where Colin, a keen guitarist, can jam with mountain musicians.
The walk starts at Springer Mountain in Georgia and takes Tom and Colin north, ending up at Mount Katahdin in Maine, passing through 14 east coast states along the way.
Daytime temperatures will be a pleasant 15 degrees Celsius at the start, dipping to minus five at night, but midsummer could see them walking in up to 40 degrees before autumn cools the air again.
Tom said: "My mum doesn't think I'll do it, but my dad's in awe.
"Colin's father would have been very proud."
Follow the pair's progress on http://walkforacure.terapad.com
WILDERNESS WANDERERS: Tom Gale (back) and Colin Ross (front) from Plymouth are preparing to walk 2,200 miles across the Appalachian trail
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