More than 280,000 people are expected to visit the 700-acre site at Screggan, less than 5km from Tullamore, in the next three days.
Ploughtown was developed over the past seven weeks in accordance with a site plan prepared by architect John Burgess.
It will disappear just as quickly over the next month as the infrastructure is dismantled and the site reverts to being a working farm.
The championships cost over €5m to stage and is expected to be worth €40m to the economy.
Statistics from a survey a few years ago showed personal shopping accounted for over €7m, trade purchases €9.6m, and food expenditure €9.5m — figures that have been surpassed.
A bewildering array of products and services, from gourmet sausages to space age farm machinery, will be exhibited.
Farmers and fashionastas, prelates and politicians, diplomats and daytrippers will attend the event which has grown from a small beginning in 1931 into Europe’s biggest outdoor rural feast.
Transforming green fields into a fully serviced town with electricity, water supplies, and almost 2m feet of trade space for 1,700 exhibitors was a daunting task.
Ploughtown has pavilions, shopping arcades, and marquees. It has 80 tower lights, 35 street lamps, a medical centre, first aid posts, thousands of electrical sockets, miles of cable, and a huge display of machinery valued at over €45m.
It is all linked by 30km of trackway and features a tented retail village, including a massive dome with space for more than 120 exhibitors.
TV and radio studios, ATMs, high-speed broadband, multiple catering outlets, and a centre for the use of many of the 800 media personnel accredited to the event are all in place.
More than 350 competitors will take part in ploughing classes. Some 1,000 live animals will be on show. And there will be attractions as diverse as a pig agility course, wellie throwing, and master jiving classes, lifestyle villages, a food fair, and three daily fashion shows with models from the Celia Holman Lee agency.
National Ploughing Association managing director Anna May McHugh said the event provides a national stage for showcasing all things agricultural, but also brings together people from all sectors of society, both rural and urban, to enjoy three days immersed in country living.
President Michael D Higgins will officially open the event at noon today.