San Bernadino, California A day of thanks was originally prescribed in 1621 by Governor Bradford of Plymouth Colony, Massachusetts, to celebrate the Pilgrim Fathers' first harvest. When Americans gathered to devour the Thanksgiving turkey just over a week, they might also have given a nod of gratitude to McDonald's - the burger at the heart of the American diet.

A humble lump of minced, flattened and grilled meat has become a national staple. Twenty-four out of 25 Americans ate at a McDonald's last year, and 7 per cent of the US population got their first job with the company. The international impact has been astounding too: McDonald's is the biggest restaurant chain in Germany, Japan - and Britain.

The first seed of culinary imperialism was sown at a dismal street corner of an unfashionable town 60 miles east of Los Angeles. In 1940, when the Battle of Britain was blazing over the English Channel, car wars were breaking out in California. Entrepreneurs were offering drive-in everything, hoping to persuade the public to hand over their dollars.

Mack and Dick McDonald set up shop at the corner of 14th and E Streets in San Bernardino, building a drive-in restaurant that became an instant success, catering for young Californians no longer shorter of money than sense. High-school kids could grab daddy's T-bird and cruise to the hamburger stand, in the fashion later described by the Beach Boys. And the stand they cruised to most often was McDonald's.

The brothers hit upon real success in 1948 when they turned the art of serving food into a science known as the Speedee Service System. By restricting choice and maximising standardisation, they could offer a rapid turnover and low prices. The system spread so effectively that in 1974, people started buying Big Macs in sterling, and by 1990 cheeseburgers were changing hands for roubles.

I was ill-equipped to re-enact fast-food history. True, I was driving a Ford, but instead of an open-top T-bird it was a rented Escort, without so much as a sun roof. The radio was blasting, but I was reluctant to follow the Beach Boys and'cruise just as fast as I can now', since last time I tried that in California the Highway Patrol cruised still faster and caught me.

My lack of panache mattered not a jot. When the first McDonald's opened, the queues went around the block, but last week, the site was deserted.

San Bernardino was once hyped in a hit song, an eponymous dirge that tainted the British charts in the Seventies. These days you wouldn't visit 'SB' for scenery, culture or nightlife. And you shouldn't come to see for the first McDonald's, either. The home of the Speedee Service System has been demolished; the original Golden Arches have long fallen.

I looked around to see what could be salvaged from the mission. But 14th and E is a corner in the middle of the economic no man's-land between town centre and suburban malls. Were SB an actual city, this would be pure inner-city squalor. The only business that appears still to be functioning is Mrs T's Rent-to-Buy.

As I photographed the site, a solitary pedestrian approached. She vetoed any possibility of conversation by yelling 'You crazy?' and crossing the street.

I hadn't made it as the new kid in town. So I handed the Escort back to Hertz, and flew east to pick up the trail.

Des Plaines, Illinois Catch a bus from the world's busiest airport, and you end up at the first link in the the world's busiest chain of hamburger restaurants.

'Dez Plains', as the locals insist upon calling it, is a pretty and self-satisfied suburb. On a bright, chilly November day, when the pale sun dwindles through the twigs of tall, balding trees, it's easy to see why Des Plaines is a desirable address.

Frank Lloyd Wright wrought architectural miracles close by, but they never quite made it here. Instead, conventionally opulent bungalows are sprinkled around the boating lake. The middle-class serenity is impaired only by the proximity of Chicago O'Hare airport, a 15-minute ride away.

The bus runs along a highway that seems to shout 'Eat]' and 'Drive]'. Just Tires, Midwest Automotive and Carx Muffler & Brake jostle for the motorist's attention with Burger King, Taco Bell, and what turns out to be the world's 1,000th McDonald's. People like to drive, and to eat, and McDonald's presented the chance to combine the experience.

The man who recognised the rich seam the McDonald brothers had struck was Ray Kroc, an Illinois-based salesman of catering equipment. The McDonald brothers were big buyers, and Kroc wondered how a single restaurant could afford so many milk-shake mixers. So he flew west to find out. He secured a franchise from Mack and Dick, and opened his first restaurant on Lee Street in Des Plaines in 1955. So central is Des Plaines to the McDonald's story that it is home to the 2,000th branch as well as the 1,000th, and also the first McDonald's-as-we-know-it.

As it slides into middle age, Ray Kroc's first McDonald's still looks spruce: the red and white tiles have lost none of their shine and the interior is spotless, and the staff sport not a single hair out of place. You can peer through the glass to admire the miracle of the Speedee Service System. But these clean-cut all-American boys, busying themselves with short orders, are mere waxworks.

Ten years ago, the Des Plaines prototype for an eating revolution had outlived its commercial usefulness. Rather than bulldozing the site, however, this piece of Americana was preserved as a museum - dedicated to Ray Kroc. The founder of the McDonald's Corporation is described on a plaque as 'Leader and Friend'. Quoted in the definitive work on the company *, Kroc's corporate evangelism sounds terrifying: 'We will make conformists out of them . . . The organization cannot trust the individual; the individual must trust the organization.'

The order pads used by the imitation staff are examples of this philosophy. At the top of each sheet is the instruction to ask, 'May I help you Ma'am (Sir)?', and at the foot, 'Thank you, please call again'. When he wasn't standardising human behaviour, Ray Kroc took a keen interest in the weather, one of the few things he realised he couldn't control. According to the ledger, Day One - 15 April 1955 - was cold and cloudy; he took dollars 366.12.

Soon, however, McDonald's had hamburger sales running into seven figures: 'Over One Million Sold', boasts the sign outside. The sign opposite reports rather better figures: 'Over 95 Billion Sold'. In 1955, an All-American Meal - hamburger, fries and milk shake - cost 45 cents (30p). In 1993 the price has increased to dollars 3.26 ( pounds 2.09), as you discover when you step across the road to a working McDonald's.

The man behind the counter winced when I ordered. 'I can do the shake for you right now,' he warned, 'but the burger will take two minutes, and the fries could be three.' What culinary-chronological oppression was wrought upon the world by the first McDonald's, I wondered, as the corporation moved one nearer to that 100-billionth burger.

I was prepared to waive instant gratification, and to wait 120 or even 180 seconds. Customers can fill the time productively, because the restaurant serves as a repository for McDonald's folk history. The first company billboard is on display, showing a woman being offered a burger, with a speech bubble saying, 'try this for sighs'.

Political correctness has crept into the American fast food diet. The Des Plaines menu includes a broccoli cheese salad, and there are rumours of the imminent appearance of a McLean Deluxe veggie burger. Ray Kroc, who died in 1984 aged 81, might turn in his grave at the prospect of teenagers taking daddy's T-bird for some soya protein and salad. To see where the All- American Meal still thrives, you need to catch a train to downtown Chicago.

Chicago, Illinois From the corner of Clark and Ohio Streets in Chicago, you can see the world's two tallest buildings. You can also see an array of energetically American restaurants competing fiercely for the diner's dollar.

Ray Kroc's tradition is represented by the Rock 'n' Roll McDonald's, a drive-in loaded with Fifties and Sixties memorabilia. Younger pretenders are dismissed with a sign saying 'On the first day He created McDonald's . . . on the second day He created Ed Debevic's and the Hard Rock Cafe'.

The competition here is getting as hot as a flame-grilled burger. The Hard Rock Cafe - based on an original lunch in Piccadilly, London - has staked its place with the others alongside McDonald's in an area of Chicago called River North.

Five years ago the northern fringe of the Chicago River was dangerously derelict, the sort of urban wasteland that gave inner cities a bad name. But despair has moved westward, and River North has become a fast-foodie's heaven.

Planet Hollywood lies at the intersection of Clark and Ohio, Hollywood hype, science fiction and gastronomic fantasy. Arnold Schwarzenegger and his partners, who run Planet Hollywood, square off against Michael Jordan. The basketball star's new restaurant is perched along the street and on the cusp between sport and short orders. Jordan's venture into Speedee Service is hard to miss, since a ball 30 feet across has been bounced on to its roof. 'The Restaurant', as it is concisely known, opened last month serving Fastbreak Fingers with Freethrow French Fries.

You can breakfast, lunch and dine out on a whole range of themes, but even the most dedicated diner should intersperse Double Dribble Cheese Fries with the sights of the greatest American city. Chicago manages to combine superlative architecture with superb humanity. The skyscraper was invented here in 1885, and a century later the Sears Tower and John Hancock Center - respectively the tallest and second-tallest buildings in the world - clawed one-third of a mile into the heavens. Chicago's skyline is majestic, but never overwhelming.

The best way to enjoy the magnificent collusion of styles and scale is from the El, as the Elevated Railway is always known. This antiquated public transport system resembles an escaped fairground attraction. It clanks around the heart of Chicago, turning impossible corners and revealing improbable views.

To escape back to a world where Coke is just a soft drink, head for Ed Debevic's 'Short Orders Deluxe'. Even if the burgers were not bloodily tasty and the fries delicious, the restaurant would be worth visiting for its entertaining menu, which ends with: 'Not responsible for lost or stolen articles, bad punctuation or misspelled words'. Even though the hamburger chains have got their teeth into the nation's appetites, Ed shows human imperfection has a place alongside Speedee Service.

*'McDonald's: Behind the Arches' by John F Love (Bantam Books, out of print)

(Photograph omitted)