The National Sod House Society promotes conservation but lacks the funds to do so effectively.

ECONOMIST: Building houses

Now known as the Sod House Museum, it is open to the public six months a year and attracts nearly 60, 000 visitors.

ECONOMIST: Building houses

It is no longer easy to build a sod house, though that didn't stop Merle Block from trying it himself about a decade ago.

ECONOMIST: Building houses

The 180-member National Sod House Society, located in Holdrege, Nebraska, sponsors field trips to sod houses, as well as model-building and essay-writing by local youngsters.

ECONOMIST: Building houses

Mr Block does not live in his sod house though he has brought his grandchildren, nieces and nephews to spend the night on beds with corn-husk mattresses.

ECONOMIST: Building houses

Mr Block, who manages a Pony Express station in Gothenburg, Nebraska, decided to build a sod house of his own after studying letters from his ancestors, who came from Germany, and those of his wife Linda, from Sweden.

ECONOMIST: Building houses

He looked at a collection of settlers' photographs taken in the late 1800s by Solomon Butcher, whose work is by far the most important documentary tool for sod-house researchers.

ECONOMIST: Building houses

It took him and a 16-year-old neighbour three weeks to pile 1, 400 pieces of sod in all, 78 tonnes of material into a house of less than 200 square feet (18 square metres) with walls that were three feet thick.

ECONOMIST: Building houses