On the road: following Jack Kerouac across the United States

Kerouac inspired a generation. Now, with a film version imminent, Steve Turner follows the original route

Car trouble: Sam Riley and Garrett Hedlund in the film version of On the Road (Gregory Smith)

Long journeys on Greyhound buses are primarily for people who are too large, poor, incapacitated, noisy or overloaded to take a plane.

Few people take them for the sheer pleasure of staring out at the rich American landscape. The 3.30pm departure from New York to Chicago was full of people with walking sticks, squealing children and odd-shaped packages wrapped in polythene. For the first half of the 17-hour journey I sat next to a student in dark glasses who was returning home after an ill-fated relationship with a single mother he'd met on MySpace. The second half was shared with a generously built woman who spent her time on a mobile phone telling friends and relations about her summer job selling water, ending each conversation with a litany of I love yous that increasingly sounded more like threats than promises.

I could afford to fly, and don't yet need two seats to accommodate my buttocks, but I was emulating Jack Kerouac, who made the same journey in 1947, and recorded it in his novel On the Road – the film adaptation of which is released in the UK this Friday. He'd intended thumbing west from America's biggest city on Route 6 but got stranded in the rain at Bear Mountain Bridge without a lift in sight and had to abandon hitch-hiking on the first day.

Before my bus trip, I had followed in Kerouac's faltering footsteps. I'd taken the 7th Avenue Subway though Morningside Heights and Harlem to its terminus at 242nd Street in the Bronx. Hitch-hiking is no longer the safe option it once was, and it is banned or restricted in many states. So I took the No 1 bus to Tarrytown and a train from there to Peekskill.

I'd imagined I could walk to Bear Mountain from there, but maps can be deceiving. The cab driver who eventually took me assured me that bears still roamed its slopes. It's not true. The mountain was so named by someone who thought it resembled a sleeping bear, not because of real or imagined ursine inhabitants.

Kerouac described Bear Mountain as dismal and smoky. It's actually charmingly unthreatening. The Hudson River is spanned by a grey suspension bridge beyond which are the gently rolling hills of Bear Mountain State Park, a retreat for New Yorkers wanting to hike, bike, camp and fish. The journey by train up the Hudson River Valley had been like a day trip into rural mid-Wales, all of it within easy commuting distance of Manhattan.

Defeated by rain and a lack of traffic, Kerouac slunk back to New York and took a Greyhound to Chicago, a journey he glossed over in a single paragraph. As he had done, I rolled through New Jersey, Pennsylvania, Ohio and Indiana, most of it in the dark. It was hard to sleep and impossible to see anything other than the moon and the silhouettes of hills. At midnight, we had to change buses in Pittsburgh.

Chicago in 1947 was honking with jazz. Kerouac hotfooted it to the Loop, the central area wrapped by elevated train tracks, to catch the best of bop. Today, the Loop is deserted at night. The theatres and clubs have long since closed down. The jazz that once indicated American vitality has become the property of aficionados, experts and historians.

It's often assumed that Kerouac either drove or hitch-hiked across America. The surprising truth is that he was virtually a non-driver and most of his initial journey from New York to California was covered by bus. He did, however, hitch-hike from Chicago to Denver, at that time home to Neal Cassady, the model for On the Road's vibrant hero Dean Moriarty.

The heart of Cassady's Denver was Larimer Street, once the city's Skid Row. It was here that he frequented bars and cheap hotels and learned the art of ducking and diving while simultaneously absorbing Shakespeare, Dostoyevsky and Proust. Kerouac saw it as an edgy street full of "old bums and beat cowboys".

The façades remain, but everything else has been cleaned up. The pool halls, bars and rescue missions are now restaurants, jewellers' shops and clothing stores. Banners for Lufthansa flutter from lampposts. Wrought-iron litter bins line the pavements. The local chamber of commerce describes the area as "elegant and charming" and boasts that it "defines hip urban revitalisation".

It was while in Denver that Kerouac had an epiphany. When walking through the city's "coloured section" he watched a softball game at the junction of 23rd Street and Welton. The sight of old men sitting out on stoops and young people laughing made him wish that he was black. In his naive and romantic view, black Americans were uninhibited, joyful and true to themselves. "The best the white world had offered," he famously wrote of the experience, "was not enough ecstasy for me, not enough life, joy, kicks, darkness, music, not enough night."

I'd imagined that 23rd and Welton would be densely packed and sizzling with urban life. What I found was a bland intersection of two wide streets with no pedestrians and a lot of heavy traffic. A high mesh fence surrounded the softball pitch, now known as Sonny Lawson Field. Not a soul was to be seen on its grass.

After Denver, Kerouac took the bus to San Francisco, a city he associated with pioneers, gold prospectors and the novelist Jack London. Six of his novels would be partially set there, most notably The Subterraneans. A stay in a rundown hotel off Third Street produced the poetry collection San Francisco Blues. As with Larimer Street, this area was regenerated in the 1980s and now boasts the Yerba Buena Center for the Arts (at 701 Mission), the Moscone Convention Center and a collection of shops.

When Neal Cassady and his second wife, Carolyn, eventually moved to San Francisco, Kerouac stayed with them at 29 Russell Street on Russian Hill. The small gabled house, tucked uneasily between taller buildings, still stands on the incline off Hyde Street. Its neat chalet style belies its tumultuous history: Kerouac's affair with Carolyn, painful rewrites of On the Road in the attic room and frequent escapades with alcohol, Dexedrine and marijuana.

San Francisco could justifiably claim to be the Beat centre of America, and if there's a Beat centre to San Francisco it's City Lights Bookstore on Columbus Avenue. It was opened by Kerouac's poet friend Lawrence Ferlinghetti in 1953 and is still run by him. It specialises in poetry, fiction, small magazines and liberal-left politics, with a healthy collection of Beat literature. To the left of City Lights is an alley that had its name changed in 1988 from Adler to Jack Kerouac.

Up the street, at 540 Broadway, is San Francisco's first Beat Museum (established in 2003). Part bookshop, part display and part re-creation of a 1950s Beat "pad", it was established by Jerry Cimino, a Beat fan and collector of memorabilia. What it lacks in professionalism and funding it makes up for in enthusiasm.

In an age of backpacking, adventure travel and extreme sports, the "wildness" of On the Road no longer shocks. Yet Kerouac inspired a generation to search for country, self and spiritual enlightenment by taking off with a backpack and not too many plans. The hippie trail of the 1960s and present day gap-year travel both owe something to Kerouac.

Al Hinkle, the only On the Road traveller still alive (he appears in the novel as Ed Dunkel and is played by Danny Morgan in the film), now lives in San Jose. I called him up and he told me about the days when America was laced with two-lane blacktops rather than interstate highways, and when hitch-hiking was as safe as public transportation. "We mostly travelled to see what was on the other side of the hill," he told me. "We were getting our kicks before we settled down. Jack was a little different, though. He was always looking for America. I was just going along and accepting it."

'Jack Kerouac: Angelheaded Hipster' by Steve Turner is published by Bloomsbury (£10.99). The film of 'On the Road' is released on Friday. The British Library displays the full 120ft manuscript scroll of 'On the Road' until 27 December.