EASTABOGA, Ala. — In the midst of one of the great natural gas drilling booms in the nation’s history, millions of Americans are struggling with a problem that is chilling their bones.

There is not enough propane, a byproduct of natural gas production and crude oil refining, to heat their homes and keep their farms running. Even while production of the fuel is up 15 percent over a year ago, inventories are now nearly 50 percent lower than last winter, and many Southerners and Midwesterners who depend on the fuel are angry and confused.

In North and South Dakota, the shortage has become so acute that the Standing Rock Sioux Tribe has opened shelters to serve its population, most of whom rely on propane. Several states have moved to help ease delivery problems, and a number of attorneys general have called for investigations into price gouging.

“It’s not a good subject right now,” said John Flanagan, a retired truck driver who uses propane to heat his home in Iowa, where the federal government said the price of a gallon had increased by nearly $2 since November. “Everybody you talk to, they’re just devastated. They’re disgusted by the whole situation.”