Generations of farmers in the flat expanses of the American Midwest have wrested a living by growing corn, collecting federal subsidies or by raising pigs. Now, increasing numbers are doing so by raising a glass.

In states such as Iowa, Wisconsin and the even the remote Dakotas, farmers are clearing fields long devoted to traditional crops and planting vines as the Midwest seeks to join the likes of Napa, Sonoma and New York state as the latest wine region in the US. Such is the pace of growth that in Iowa alone a new winery is licensed every two weeks.

"Iowa used to be a large grape-growing state but prohibition killed it off," Stan Olson, owner of the Penoach Vineyard in Adel, said. "Now I think there are between 70 to 75 wineries in the state."

The new vintners of the American cornbelt say they have been pushing against something of an unlocked door. Not only are they making money from selling wine but the wineries have become a tourist attraction in their own right.

Mr Olson's business, which also sells grape plants to would-be growers, opened a tasting room in a converted barn three months ago.

"On the East Coast you've got mountains, oceans and big cities. There are plenty of opportunities for tourists," he added. "But in Iowa we don't have anything like that. People are looking for something different to do."

But whether North America's more established wine regions need to be concerned about the threat from this upstart is a matter of some dispute, despite the region already showing impressive results. Earlier this year a wine from Ohio - the 2005 Grand River Valley Golden Bunches Dry Riesling produced by the Ferrante Winery - won the top prize for white wine at the Riverside International Competition in California.

But given the harsh winter climate of the Midwest, the majority of the vineyards only grow so-called hybrid varietal grapes rather than the more widely recognised European grapes, such as cabernet sauvignon or chardonnay. As a result visitors to the region's wineries are more likely to find themselves drinking vidal blanc or chambourcin.

Gail Nonnecke, a professor at the University of Iowa's Department of Horticulture, said: "We have hybrid varieties which have the quality of the European grapes with the hardiness of the American species. That is why we are able to grow them. We have some wonderful wines that have an excellent taste."

While Iowa has received most attention for its wine boom - the state recently appointed its first full-time oenologist - the growth has had an important impact across the region.

The burgeoning wine industry in Indiana has added $34m (£17.5m) a year to the value of local economy and the number of wineries in South Dakota has more than doubled, although the total still stands at a modest 11.

The growth of vineyards is also providing opportunities for young people. Corey Goodhue, whose family grows corn and soybeans on 3,300 acres near Des Moines, Iowa, is turning to grapes to help the family business. "We're not getting enough value out of corn and beans," he told The New York Times. "On one acre of ground, if we net $40 with corn or beans we've [done well]. With grapes, you could net upwards of $1,500 per acre. Growing grapes is the holy grail of high-value crops."