After landing at O'Hare International Airport in Chicago, I spend more than two hours in rush-hour traffic to get to my hotel in Milwaukee, Wisconsin. Fifteen minutes later, I am driven to several acres of purpose-built park boasting numerous stages, a cultural village, hundreds of stalls purveying all things Irish and several thousand punters, of all ages, wearing a lot of Kelly green.

The dreaded C-word adorns every hoarding. There are shamrocks, shawls, harps and hurleys, as well as a Celtic cross in finest fibreglass to mark the crossroads leading to the town of Ballyfest. Throw in a few Celtic canines, bagpipes, flags and a T-shirt with the legend "I love my Irish priest" - with not a trace of irony intended - and you have a fair first impression.

Now add sound, from at least eight or nine stages at any given time, with amplification, all in the open air. That's a lot of music.

A line of dogs of all shapes parades past. A troupe of small girls in elaborate costumes appears from behind a tent, their blond ringlets so alike and awful that I assume they are wearing wigs.

This is no place for the purist, the jet-lagged or the faint-hearted. Either I have wandered into the Celtic circle of hell or Aer Lingus has put something potent in the tea. Irish Fest is in full swing, and Irish America is here to party.

I'm here to read poems. I have long heard talk of this, reportedly the most enjoyable Irish festival in the United States, the one many recent immigrants from Chicago and wider Illinois attend every year for the currach racing, the music and the craic.

At 10 p.m. on Friday, I think they are all mad, that this is an elaborate excuse to sell beer, like most of the festivals at home. It serves me right for agreeing to read poems in a tent called the Hedge School, beside another tent called Moore Street, in the cultural village of an eight-acre fairground on the shore of a Great Lake.

However magnificent the setting, this festival is a cross between a Ballinasloe horse fair and a Slane concert, held in the land of the plastic Paddy, where contests for freckle-faced children, sideshows and freak shows abound: Ireland abroad making the usual show of herself.

Yet over the next two days I see another side to a culture expressing itself in a neutral place, and come to understand that the neutrality of the venue is liberating.

There is a carnival atmosphere at Milwaukee Irish Fest, with large numbers of children and teenagers, for whom there is an extensive programme of activities. Celebrating its 21st anniversary this year, it is the biggest Irish festival in the US, attracting 30,000 visitors a day and run by a staggering 4,000 volunteers and only two staff.

It is well organised and well worth the $10 admission (children under 12 get in free), which covers the whole day and all events.

The only alcohol sold is beer, for which Milwaukee, with a population of about 600,000, is famous. Visitors can and do buy goods ranging from hurleys to books from the 90 stalls selling their wares and services, making this an important trade fair for Irish businesses.

The heart of the festival is the music, and a huge crowd gathers for the Eileen Ivers concert on Saturday night. This brilliant fiddle player is appearing in two concerts, fronting her band. They come onto the stage to loud applause and launch into a high-voltage set, Ivers dancing and weaving like a demented imp.

She electrifies the crowd with a dazzling show of virtuoso playing, turning first to one, then another member of her band in a high-speed musical conversation.

Then she focuses her attention outwards to the audience, who shout and cheer and answer her calls in a deafening chorus.

Her famous blue fiddle seems an extension of a vibrant personality, a player so sure of herself and her instrument that she can cut fast and loose with the tradition she was raised in.

She is curious and open to new influences in a way that is musically exciting, taking her fiddle to a heady edge. If occasionally she goes too far and slips over the edge, what of it?

She speaks of playing on the Caribbean island of Montserrat to an audience of black Irish, and introduces Tariq, an African-American dancer whose style is reminiscent of that of Galway's Ray McBride. When he later joins the line of young girls in a Riverdance-style performance, there is humour as well as delight in this dance with a difference.

The audience, too, is growing more diverse each year. Tom Commiskey, from Illinois, and Ody Madison, his African-American-Indian friend, have come for the music and are delighted by the performance of the young Irish band Dan·.

This is Commiskey's fifth visit, Madison's second. In a city that has experienced considerable racial tension, he feels comfortable at the Fest. "This is a neutral territory where people don't feel threatened," Tom says.

They'll be back next year.

In the cultural village at the quiet end of the grounds, the Gaeltacht tent is perhaps the closest to home in terms of atmosphere. An array of artists sing, dance and play with humour and grace. The audience listens, chats and laughs at a macaronic song about "www.diddly-aye.com", performed with vaudevillian aplomb by two members of Grupa an Oireachtas.

Construction workers from Chicago, who make up 50 per cent of the festival audience, gossip in Irish with friends and strangers alike. There is an ease here, rooted in words.

"An essential part of their identity for young Americans is the search for an ethnic culture," says John Gleeson, the festival's cultural adviser. "They want to explore that. This is why the cultural village is so important".

A man of vision, Gleeson fights to continue and broaden the impressive programme, which includes drama and poetry as well as history and archaeology.

He believes it necessary to build on the interest sparked by the music and create a deeper cultural awareness of what it means to be Irish.

At the final event of the weekend, the musicians and dancers fill the stage. They let rip with jigs and reels. The audience goes wild. This is no time for finesse. The dancers come on and there is a moment when the playing shifts, the music opens and loosens into a sound of pure joy, as if a tradition has briefly overcome its inherent constraints.

As I shut the door of my room that night, I hear a fiddle played slowly from the roof, the sound drifting out over the lake in the early morning, and a man with a beautiful voice is singing Eileen Aroon in the ballroom a floor below.

Tomorrow the Irish will be gone, Milwaukee will welcome the Indians, the Germans or the Italians and the show will start all over again.

Mary O'Malley is a poet; she is working on a memoir