These stony-faced people are world-famous, but who are they? And where are they?

Well, the little brooch worn by the woman seems to depict Persephone, the Queen of the Underworld in Ancient Greek mythology.

The man's pitchfork, then, may be a reference to Pluto (or Hades) the King of the Underworld, who abducted Persephone and brought her there to be his wife.

A trident was part of his iconography.

And so this striking vision of rural America might be some sort of allegory for the Underworld, with these severe and rather hostile farmers its King and Queen.

Or not. This is a mysterious and compelling painting and nobody can agree about what it represents...

There will never be a definitive answer - Grant Wood himself wasn't clear about its meaning, or whether they are man and wife or father and daughter.

But there's one question we can answer: why does it look like that?

Grant Wood was born in 1891 in rural Iowa. Ten years later, after his mother's death, the family moved to Cedar Rapids.

He worked at a metal shop and then studied at arts and crafts schools in Minneapolis and Chicago before becoming a public school art teacher in Cedar Rapids.

In the 1920s, while working as a teacher, Wood made several trips to Europe, including a year studying at the Académie Julian in Paris.

There he adopted an Impressionist style; his charming but unremarkable paintings from that time are unrecognisable from the Wood we know today.

Everything changed in 1927.

Wood, as a local artist, was commissioned to make a stained glass window for the Cedar Rapids Veterans Memorial Building.

But he knew little about stained glass. So Wood travelled to Germany, where he planned to work with its glass experts.

He did. But something else happened. He was exposed to the work of 15th and 16th century painters from the Netherlands and Germany.

Here's a portrait by one of them, Hans Memling. Notice her severe expression and the astonishing attention to smooth, minutely realised details.

Wood was inspired by those serious portraits and found in them a comparison with his home in Iowa.

But he also fell in love with the infinitely receding landscape backgrounds of artists like Rogier van der Weyden, with their smooth rolling hills and cities like little models.

Early Netherlandish art, with its excruciating attention to detail, was almost photorealistic. But it was highly stylised at the same time, both realistic and unrealistic at once; nature beautifully realised but not quite natural.

And the humans are all rigid, solemn figures.

Back in Iowa, passing through the town of Eldon, Wood saw something:

"A trim white cottage, with a trim white porch — built on severe Gothic lines. This gave me an idea. That idea was to find two people who, by their severely strait-laced characters, would fit into such a home."

In the end Wood found two models: his sister, Nan Wood Graham, and the local dentist, Byron McKeeby.

Wood had the chance to put his new, Netherlandish-influenced style into practice: the stylised realism, the severity and gravity, the smooth details...

He sent it to an annual exhibition at the Art Institute of Chicago, where he won the Bronze Medal and $300 in cash.

But that's not all. American Gothic was a sensation. Wood had been an obscure, regional artist. This painting brought him overnight national fame.

The image was reproduced tens of thousands of times and rapidly became the most famous work of art in the country.

Here, the critics said, America finally had a proper American artist. None of that European stuff, of which Wood himself had, as we saw, once been a proponent.

Still, nobody could agree about what American Gothic meant. Some saw it as a brutal but brilliant satire of rural America.

While others found in it a perfect testament to the sturdy, hard-headed, honest, unselfconscious virtues of country life, away from urban corruption.

Well, Wood continued with his newfound style, infusing those idyllic landscapes from the Early Netherlandish masters with his own sense of the American landscape.

No wonder the set designers of the Wizard of Oz were inspired by Wood's art.

And yet, with its smooth intensity, Wood's unusual and highly idiosyncratic style can seem almost Surrealist at times, as if from a dream.

Delightful and vivid and charming but, somehow, otherworldly. Wood was an artist with a singularly striking visual language.

The Midnight Ride of Paul Revere, from 1931, is one of his finest paintings.

Here, more than anywhere else, we can see Wood's talent for turning a landscape into a set of models, with houses and trees and humans like toys.

He even painted what seem like testaments to the alterpieces and triptyches of those 15th century painters he so loved, with their extended scenes spread across several locations and seen from an impossible perspective.

Only here we see rural life rather than Medieval saints.

When Wood completed that stained glass window back in 1927 members of the local branch of the Daughters of the American Revolution complained that he had gone to Germany for inspiration.

Because the window was in memory, partly, of soldiers who had died fighting Germany in WWI.

It was in response to this reaction that Wood painted Daughters of Revolution in 1932, an obvious satire and perhaps the only time Wood ever fully revealed himself in his art.

Here we see Wood's capacity for rather ruthless irony. Is it present elsewhere in his work?

Well, Wood remains an elusive artist. His paintings are both charming and artificial, a delicate evocation of nature and an ethereal, dream-like vision of it, for some beautiful and for others slightly disturbing.