It's the middle of the afternoon and I'm half cut. Since about 11:30am, I've been rumbling through Denver's River North district (RiNo), weaving my way through several blocks of regenerated low-rise industrial buildings that have been turned into food markets, distilleries, breweries, urban wineries and trendy stores full of sunglasses, rolltop backpacks and brightly coloured outdoor clothes. Along the way, I've tried board after board of 20cl beer tasters: I've lapped up juicy New England IPAs made with flaked oats, West Coast hops and crisp Colorado mountain water; I've sipped porters aged with vanilla pods in Kentucky bourbon barrels; and sampled spritzy saisons while watching locals play shuffleboard and cornhole in the afternoon sun.

What to expect from the Colorado beer tour

My ride until now – an electric tuk tuk driven by my obliging guide Chris – has just whirred off into the distance and become a mirage in the 25°C heat. But for some reason, despite being alone, a little overheated and ever-so-slightly inebriated, I don't feel stranded. Yesterday I was slugging it out among holidaymakers at Gatwick airport; now – courtesy of a relatively new direct flight route to Denver from Norwegian – I'm here in RiNo, the beating heart of the city's incredibly well-established craft beer scene. Among the street art, alleyways and taproom patios slowly filling up with the Friday afternoon trade, I feel like I'm in good company.

Sandwiched between the rippling wall of the Rocky Mountains to the west and more than 500 miles of plains that roll through Kansas and Missouri to the east, Denver – and its nearby front range cities Fort Collins, Boulder, Loveland and Longmont – are a bastion of progressive politics. Cannabis has been legal in the state of Colorado since 2014, and a vote this May effectively decriminalised magic mushrooms in the city of Denver. It's these politics, the incredibly high-quality mountain water, and a series of alcohol laws that barred booze from being sold in chains and encouraged people to head to their local brewery tap that makes Colorado an incredibly fertile ground for beer producers. The state, alongside others like California, Oregon and Michigan, has experienced a boom from the 1980s to today.

Home to just 620,000 people, the Colorado beer tour can consist of up to 80 locations - Denver has roughly this many breweries and brewpubs,  whilst London has about 100 for 8.8 million, in contrast - and more than ten of them are in the RiNo neighbourhood alone.

Colorado beer tour: A beer tour of Denver

There are brewers like Prost, who make beer to the strict rules of the German Purity Law, using only water, hops, malts and yeast. There are brewers like Mockery, who set out to make beers that deride such rules with their adjunct-laden range of lemon meringue IPAs, chai vanilla stouts and black lagers infused with mushrooms. There are brewers like TRVE that make fascinatingly complex oak-aged sour ales while heavy metal blares from their taproom. And there are brewers like Crooked Stave, whose owner and brewmaster Chad Yakobson helped breweries like TRVE get there, by putting his PhD thesis on wild yeast fermentation online as a free resource for other brewers to use.

This is a rich, tightly interwoven community that's passionate about beer - hence the reputation of the infamous Colorado beer tour - and despite the high volume of breweries per person, the bars remain busy. To some degree, it's because 300 days of sun a year leaves you a lot of time to go out drinking, but it's mainly because the average Colorado resident's palate for craft beer is, it's probably fair to say, a bit more refined than ours. Head to Union Station, the neon-clad centrepiece of brushed-up downtown Denver, and you find the 30-tap Terminal beer bar in its main concourse. This isn't a bar serving baseball beers from huge multinationals, either – instead, its taps pour saisons and sours, brut IPAs and Belgian-style dubbels – some brewed just a couple of blocks away.

"It's estimated that 11.6 gallons of craft beer is consumed per person in the state of Colorado each year," says Crooked Stave marketing manager Jennifer Wolinski, sipping at a glass of vinous peach sour across the table from me in the brewery's taproom at The Source market in RiNo, "everyone knows about it, and everyone wants to learn more." It's that thirst for knowledge that's allowed Crooked Stave to focus most of its efforts on slow souring and artisanal blending with fruit, botanicals and oak barrels from the wine and spirits industry. It creates beers like Vieille, a saison modelled on old-school beers from France and Belgium that sings with green-apple tang thanks to being secondary fermented in an oak foeder (essentially a large barrel), but it also makes wild beers like Crooked Peachie O's, which uses Colorado peaches and crystal hops to emulate the fizz and tang of the sweets of the same name.

It's estimated that 11.6 gallons of craft beer is consumed per person in the state of Colorado each year

"We have an entire board of 'clean' beers for people that want to come in and drink lagers and IPAs," continues Wolinski, gesturing to a second board to the left of the one I've just ordered from, "but most people come in and ask us questions about our sours, and they can get pretty technical."

It's also that knowledge and interest that's helped elevate beer from the realm of the dive bar – or, to find a London equivalent, the humble railway arch taproom, to the main focus of the flagship bar in a mainline train station or the top-floor terrace of a luxury hotel development, putting it on a level with 'fancier' drinks like wine or cocktails. And that's exactly where I am half an hour later: on the eighth floor of The Source Hotel, a minimalist, chic property next door to the food market Crooked Stave has taken up residence in, and one that's home to a shiny new pilot brewery from the legendary New Belgium Brewing Company. Based an hour's drive north in Fort Collins, it's one of the old-guard breweries on the Colorado beer tour, founded in 1991 by one-time couple Kim Jordan and Jeff Lebesch after a bicycle tour of Belgium.

The brewery distributes nationally, gives millions of dollars to local charities and initiatives, remains fiercely independent and employee-owned, and is responsible (at least in part) for the popularity of Belgian-inspired wild beer in Colorado, thanks to its huge barrel-aging and blending programme. For that reason, it needed a different way into the booming, boutique beer scene of RiNo than just serving the beers from up the road in Fort Collins – and so entered The Woods.

Part of the Colorado beer tour includes an upscale rooftop bar with a whopping 48 beer lines, a large outdoor terrace and a row of barrels for aging beer made at the brewery downstairs; The Woods offers panoramic views towards downtown Denver and out across the foothills to the jagged peaks of the Rocky Mountains. The spot's special feel is underlined by the 20ft queue forming at the bar's entrance just before 6pm, just as the sun starts its slow downward arc behind the Rockies. It offers a range of roughly 20 New Belgium beers – half of which are brewed in the lobby – and a rotating stock of other Colorado brews ranked by their distance from the bar, ranging from about 20 miles away in the town of Lafayette to a mere 350ft away at Crooked Stave.

"When you look around Colorado, or even just take a walk around RiNo, you see all these breweries doing different things," says the hotel's F&B director – and my drinking partner – Antoine Moinard, a Frenchman who was drawn to Colorado for the mountain life and converted from wine to beer by the heft of the brewing scene here "That's why this bar isn't about New Belgium, even though they're brewing right here," says Moinard. "It's about the state: it's about 14er Brewing Company and Ratio Beerworks over the railway tracks there, it's about Great Divide down the road and it's about Crooked Stave downstairs."

Colorado beer tour: Coopersmith's brewpub

But how did we get here? Sitting at a table covered in beer tasting boards at Coopersmith's brewpub in Fort Collins the next afternoon, head brewer Chris McCombs fills me in: "When homebrewing was legalised in 1978, Colorado became the epicentre of a boom of new breweries alongside Chico, California, where you have Sierra Nevada, and Anchor in San Francisco, which had been taken on by Fritz Maytag in the 1960s. It's a progressive state, it's full of universities and people are all pretty open to experimentation," he says. "It's also the birthplace of a huge homebrewer: Charlie Papazian."

As the writer of beer-making bible The New Complete Joy of Homebrewing and founder of the Association of Brewers, Papazian has helped give thousands of aspiring homebrewers the knowledge and confidence to become successful brewers through his writing and the impact of events like the Great American Beer Festival (GABF), which he founded in his hometown of Boulder to showcase 24 top breweries back in 1982. These days, a medal at GABF is pretty much the most prestigious accolade an American brewery can earn, and the festival pours more than 4,000 different beers from 800 breweries to 62,000 visitors at Denver Convention Centre each September. Things have come a long way indeed.

Later that afternoon, my Colorado beer tour leads to me pushing through the door of Purpose Brewing & Cellars, sliding past a hitched-up horse and its jodphur-clad rider before seating myself at a table among the rows of wooden barrels. Walking towards me with a beaming grin on his face, a New Belgium-branded flat cap on his head and a pair of tiny round glasses in front of his eyes is Peter Bouckaert, a Belgian brewer who moved to the US and joined New Belgium in the late 1990s after 13 years making oak-aged sour beer at the much-lauded brewery Rodenbach in West Flanders. After two decades of brewing and blending across town at New Belgium, he set up Purpose with brewer Mike Hiatt in 2017, looking to brew smaller batches of increasingly adventurous beers, more like art than production. Why? Because in Fort Collins, they were ready for it.

I slide past a hitched-up horse and its jodphur-clad rider before seating myself at a table among the rows of wooden barrels

"Back when I started at New Belgium, the American drinker was seriously underdeveloped. We were having to make beers that were accessible to Budweiser drinkers." says Bouckaert, through the thick Belgian accent he's retained in spite of living in Colorado for almost 25 years. "It was tough; you had to build expectations about sour beer by asking questions like 'Have you had wine?', and now 20 years later you have people wandering up to the bar asking what sours I have, and I say 'Yes! We got 'em!'"

Each Saturday, Bouckaert gives a small group tour of the brewery that includes a three-hour barrel tasting session. It's a beer nerd's dream: you follow Bouckaert around as he pulls nails from barrels, pouring you thimblefuls of beer for a super-exclusive tasting. You take notes, you talk about the liquid in your glass and work out why it tastes the way it does, then at the end you decide which of the beers goes on tap for punters at the tasting room the following weekend. Many of these beers, racked in a floor-to-ceiling store of barrels, will become what Bouckaert calls smoeltrekkers: an obscure Flemish word that loosely translates to 'face-puller', it's used to describe the funny faces pulled by the first-time sour beer drinkers encountered when he first moved to the States more than two decades ago.

And this is just one of Fort Collins's 24 breweries: scattered across the Old Town square and its leafy residential roads you've also got breweries like Odell, established back in 1989 and among the very first craft breweries in the state. Then you've got new breweries that don't do any brewing at all, like Jessup Farm Barrel House, which receives its wort from sister brewery Funkwerks across the way, then ferments and ages it in tank and barrel for its tap house on the edge of town.

It's not just here you get it, either – the Colorado beer tour has upwards of 150 breweries to discover: a 40-minute drive south in Longmont you can sweep through 13 of them on the Brewhop Trolley, a bus service that'll drop you at the tap rooms of esteemed breweries like Left Hand and Oskar Blues. In Boulder, you've got tonnes of brewpubs, the Upslope Brewing Company, plus the hulking out-of-town facility at Avery Brewing Co (now owned by San Miguel), which has two bars, a restaurant and a programme which explores recipes of antiquity, from the beer of ancient Egypt to the oak-aged porters George Washington would've been drinking back in the 1700s. Even Greeley, an industrial town half an hour from Fort Collins that's famous for its meatpacking plant, is home to Weldwerks, which makes one of the most celebrated IPAs in the whole of the USA – a thick, fruity hop bomb called Juicy Bits.

Back in Denver, after touring all of the above and more, I head to Liberati, an upscale Italian restaurant and microbrewery that focuses on a world first: oenobeer. Made with up to 49% of its fermentables coming from grapes, it provides a canvas of experimentation in an area in which breweries are increasingly running out of room to play. Arriving in a series of tiny wine-tasting glasses, an 11.6% Belgian strong golden ale called Sogni D'Oro – usually spritzy, fruity and spicy – is augmented with marsanne and gewürtztraminer grapes from Washington and Oregon to give it a flinty minerality, while a 13% New England-style DIPA is fermented with malbec grapes to add notes of strawberries, cherries and some tannic, vinous funk to a beer that's usually soft, juicy and simple. To properly process them, you have to rewire your brain to understand the flavours and mouthfeels: the textural complexity, the flavours you expect, and the ones the grapes mask and replace.

Getting there

Norwegian flies from Gatwick to Denver from £410 return; norwegian.com.

Craft your Colorado beer itinerary at colorado.com, denver.orgvisitftcollins.com and bouldercoloradousa.com.

The strangest thing about them, though, is that they're the only kind of beer I try in Colorado that I've never seen in the UK. But while we've got all the same styles – the vast swathes of New England pales, the bold imperial stouts, the tallboy cans of brut IPA and the lip-puckering sours – what we haven't got just yet is the cultural structure that makes the Colorado beer tour quite so well developed. It may take some time until we've got a destination bar serving 30 taps of local, independent and forward-thinking beers in Paddington station – but if the Colorado blueprint is anything to go by, we've got a lot to look forward to.