The “stone belt” (also called the “kidney stone belt”) is the area of the United States where people experience the most kidney stones. The term “stone belt” dates to at least 1976, when the belt was determined to be in the Southeast.
 
In July 2008, two University of Texas researchers released a study showing that kidney stones flourish in warmer climates, especially when a individual moves from a colder climate to a warmer one and experiences dehydration. It is unclear if Texas is formally in the “stone belt” (some researchers say that the belt stops at Louisiana), but Texas is definitely a warm climate.
 
         
Wikipedia: Kidney stone
Kidney stones, also called renal calculi, are solid concretions (crystal aggregations) of dissolved minerals in urine; calculi typically form inside the kidneys or bladder. The terms nephrolithiasis and urolithiasis refer to the presence of calculi in the kidneys and urinary tract, respectively.
 
17 June 1976, Danville (VA) Register, “Danville In Middle Of ‘Belt” Where Kidney Stones Prevalent,” pg. B1, col. 5:
In Danville, which lies near the center of America’s “kidney stone belt,” males should be quite understanding about the pains of childbirth.
(...)
Completed last year under the direction of Dr. Ralph R. Lands, the clinic’s study used information supplied by 285 American hospitals to show that the Southeastern states definitely form a “stone belt.”
 
The belt extends from Washington, D.C., on the north to Florida on the south. It runs from about 50 miles inside the eastern coastline to the crest of the Appalachians.
 
24 March 1984, Miami (FL) Herald, pg. 2BR:
That’s especially good news in the Southeast, known among urologists as the “Stone Belt” because of its dramatically higher kidney stone rates. 
 
30 July 1985, Atlanta (GA) Journal-Constitution, pg. A20:
The Southeast - Georgia in particular - is known as the “stone belt” because kidney stones are nearly twice as common in the region as they are nationwide.
 
21 June 1999, Albuquerque (NM) Journal:
New Mexico is in the “kidney stone belt” that runs across the southern United States, according to Dr. Stephen Lucero, a Santa Fe urologist. “It’s because of the heat, basically,” he said.
   
21 June 1999, Fayetteville (NC) Observer:
North Carolina is in the Kidney Stone Belt, where the incidence rate is higher than in any other section of the country.
     
Montreal Gazette
Global warming may expand U.S. ‘kidney stone belt’, say scientists
Tom Spears , Canwest News Service
Published: Monday, July 14
OTTAWA - One of the first direct impacts that global warming has on our health may hit us where it hurts: In the kidneys.
 
People will develop more kidney stones in a hotter climate, because the heat tends to make us dehydrated and that causes the stones to form, two Texas urologists say.
 
Drs. Margaret Peale and Yair Lotan of the University of Texas say there’s already a “kidney stone belt” in the hot, humid U.S. southeast, stretching from Louisiana to Florida and north to Tennessee.
(...)
The link between temperature and kidney stones is well known, Peale said.
 
“When people relocate from areas of moderate temperature to areas with warmer climates, a rapid increase in stone risk has been observed. This has been shown in military deployments to the Middle East for instance.”
 
It’s the second recent piece of bad medical news for people in the U.S. Southeast.
 
In June, researchers reported that this area is also a “stroke belt,” where the risk of stroke is about 10 per cent higher than in other regions, and even visiting increases the risk of a fatal stroke.