Lilly Quinn and Sarah Little managed to do it without spending a dime beyond their £300 flights from the UK.
They spent five months travelling thousands of miles across 48 states, taking in some of the most epic landscape on earth.
"We wanted to do something challenging," explains 29-year-old Lilly.
So how did they do it? They hitch-hiked, couch-surfed and even used Tinder. Here are their top tips.
Take the leap, just go for it
"Having no money meant we were pushed to get out there and meet as many people as possible," Lilly explains.
Sarah, 25, was inspired to take on the trip after reading On The Road, by Jack Kerouac, a classic book about hitchhiking.
"I posted on Lilly's Facebook saying 'How do you feel about hitchhiking? And America? And the book On The Road?'
"She just replied, 'When are we leaving?'"
Do your research... all the time
The girls began their trip in Boston, using a "free couch" website to get their trip going.
Every morning, they would spend up to an hour online searching for free things available to do in the place they were staying.
"My favourite experience was just seeing every day America," says Lilly.
"Staying in a squat in Detroit or volunteering at a pay-what-you-can cafe in Denver, they were real highlights."
Find people, projects... and leftovers
One of the first meals Sarah and Lilly managed to get was from a man who posted online about leftover food in his fridge.
Most of their food was sourced through social networks or volunteering at projects they found along the way.
They also got free food samples from shops along the way.
And some of the lifts they blagged came with a kindly driver who treated them to a meal.
"We went away with bin bags full of pastries which was great, we lived off them," Sarah tells Newsbeat.
On one occasion they pretended to be students to get into a "chocolate science lab" taster session at Massachusetts Institute of Technology.
'It wasn't always easy'
Sarah tells Newsbeat "we went three days without a proper meal".
She explains: "We did have a small sweaty lump of cheese and some trail mix but no actual meal so that was pretty tough."
The pair ebe tried bin-diving and scavenging for leftover food outside supermarkets and restaurants.
Be creative and (maybe) use Tinder...
Sarah and Lilly relied on sleeping on people's couches, but had six nights in hotels paid for by strangers.
They also spent two nights in a truck, six in a tent they had brought from home as a back-up, and even used dating apps.
"We decided to try and use Tinder, swiping right for everyone within a 1km radius," Sarah says.
"A couple of guys were a bit creepy, but we found one really lovely one who let us stay.
"He'd spent some time on the streets himself and said he hated the idea of us having to sleep rough."
Spread the word
Sarah and Lilly went to baseball games in Chicago and joined party buses in Vegas.
They scored the bus trip for free through a friend, when two members of her group couldn't go because they were under 21.
They also got chatting to the people who gave them lifts - who also had friends in other states that could help.
As word spread more and more people heard about the challenge and wanted to help out.
Now they're back home, the girls say their experiences have taught them how generous strangers can be.
Sarah tells Newsbeat "we were blown away by the kindness of people on our trip".
It also made them realise "how easy it is to spend unnecessary money, when actually there's plenty to do for free".
Lilly says "at some point, I'd like to try and live a completely sustainable life. And if I can see a whole country for no money at all, then why not?"