Since 2000, the centre has been slipping away from Edgar Springs
As the number of people living in the United States hits 300 million, the BBC News website's Matthew Davis visits a tiny Missouri hamlet known as the "population centre" of America.
Here in Edgar Springs the United States does not feel like a country of 300 million people.
This is a blink-and-you'll-miss it kind of town - with a population of 190, little more than a petrol station and a few dozen houses at an isolated crossroads on the edge of the Mark Twain National Forest.
Six years ago, Edgar Springs experienced a brief moment of acclaim, when the US Census Bureau proclaimed it the new "population centre" of the US.
That is the notional point at which a flat-surface representation of the US would balance if everyone counted in the 2000 census stood up in their homes.
The distinction - calculated every 10 years as an aid to understanding population distribution - is marked by a small plaque outside the town's cemetery.
But really this swathe of the Mid-Western Bible Belt is more like the hole at the centre of a "population bagel".
At 0746 (1146 GMT) on Tuesday, the census bureau will announce that the 300 millionth American has arrived - born, or crossing a border near one of the burgeoning West Coast conurbations like San Diego or Los Angeles.
The McCurrys dream of moving away from Edgar Springs
Rural Edgar Springs is about as far removed from those cities as it could be. Only about three in every 100 Missourians was born outside the US - in California it is more like 30.
But as America tries to decide whether this relentless expansion is a good thing or a bad thing, this corner of Missouri is an intriguing microcosm of the debate.
Stephen Sowers is publisher of the local newspaper in Rolla, the nearest main town to Edgar Springs.
"We are Bible Belt, for sure," he says. "We are meat and potatoes kinds of people - this is a pretty conservative corner of America.
"But just up the road you have the University of Missouri. We get a lot of folks from all over coming there, Indians, Europeans. Sometimes they like what they see and they want to stay."
Mikel and Taffy McCurry, both 20, and their 10-month-old daughter, Stormie, live in Taffy's father's ramshackle house on the outskirts of Edgar Springs, surrounded by fields and woodland.
Taffy's father has travelled "13 countries of the world" with the US Army, but has lived in Rolla since 1974.
Despite his excursions, he says he is proud to have a very local, conservative view of the world.
"There's been more than 30 houses put up here in the last 20 years. People in these parts don't want that sort of change. If I wanted to meet 300 million Americans, I'd go and live in New York," he says.
When a retailer opened a major distribution centre 45 minutes away, "bang went the neighbourhood".
"They have quotas for employing, you know, minorities. So now we have a lot of new faces around."
But while his daughter has lived in the area all her life, her husband was born in Germany, the son of a US soldier stationed overseas - and is one of Missouri's 3% of foreign-born citizens.
Taffy loves the nearby lakes and rivers, but not the fact that there is nothing to do in Edgar Springs, or that Stormie will have to travel 20 miles (32km) to high school - or to visit a hospital.
Both she and Mikel aspire to get out, and away. "People in Rolla stab you in the back," says Mikel. "I want to go somewhere peaceful, somewhere where everyone is treated equally."
He hopes the family can one day move to Florida or California - where he can make it in computer games, where Taffy can become a furniture-maker, and where Stormie will have a life of greater opportunity.
Sense of anxiety
Even as the McCurrys dream of relocating, the geographic point of Middle America - if not the cultural mindset - is also slipping inexorably away from the town.
Edgar Springs will be the "centre of the US" until a new calculation is made in 2010. But ever since 1790, that point has been steadily moving south and west, along with the population.
Back then, there were 3,929,214 Americans. By 1915 there were 100 million, twice as many again by 1967. The census bureau predicts the US population will hit 400 million by 2042.
Such milestones have invariably provoked a sense of anxiety in some quarters. In 1968 it was typified by Paul R Ehrlich's apocalyptic tome, The Population Bomb, with its dire warnings that unchecked expansion would usher in future famines.
Today, the same doom-laden tone is heard from those warning of unchecked illegal immigration, like Patrick Buchanan, who argues that the children of 2006 "will witness in their lifetimes the death of the West".
And it finds an echo in the words of people in places like Edgar Springs all over America.
But for many in a country fed and nurtured by immigration, the ticking of the population clock to 300 million will be a cause for celebration.
"Never in the history of mankind have so many people lived such free and prosperous lives in one country," says Daniel Griswold, an immigration expert at the Cato Institute.
"As long as America remains the land of the free, a growing population will mean more opportunity and more prosperity for those of us fortunate to count ourselves among the 300 million."