POOR VALLEY lies between two ridges in the far southwestern corner of Virginia, deep in the Appalachian mountains, not far short of the Cumberland Gap through which, in the late 18th century, the back-country settlers, led by Daniel Boone, poured westward into the Blue Grass country of Kentucky.

Life has changed little in Poor Valley since Boone's time, considering that it lies within a few hours' drive both of Washington and of the industrial heartland of the Middle West. This is the poor, white, mountain South, the land of country fiddlers and pot-still whisky.

Plenty of the farmers still live in log cabins, and all of those lucky enough to hold a tobacco allotment from the government still cure their leaf in big wooden barns, bleached gray by the sun, whose design can scarcely have changed since the local men rode over the hills to fight the loyalists and their British officers at King's Mountain in 1780. In the mountain South, people bury their dead in cemeteries on their own land, and many of the cemeteries in Poor Valley are more than 200 years old. In fact, out of 119 families now living in the three-mile stretch of the valley along Brumley Creek to Hayters Gap, 118 have lived on the same land for more than a century.

The people of Poor Valley have not abandoned their old-time religion. Indeed it brings them strength in face of a new and menacing tribulation. Every few hundred yards along Rte. 689 there are placards neatly handwritten in red paint on white boards:

"Romans 10: 13. For whosoever shall call on the name of the Lord shall be saved."

"Proverbs 22:28. Remove not the ancient landmark which they fathers have set."

"Our forefathers fought for our country. So let's fight for our valley."

They will have to fight because Brumley Gap is one of two alternative sites where the Appalachian Power Company (APCO) has applied for permission to build a pump storage facility. The other is in even wilder country at Powell Mountain in the next county.

A pump storage plant consists of two reservoirs. Water is pumped up to the upper one at off-peak periods, then allowed to flow down through generators at peak. The upper reservoir at Brumley Gap would drown 620 acres of mountainside with its wild turkeys and white-tailed deer. The lower reservoir would drown the farms, churches and cemeteries of Poor Valley. Altogether the facility would cost $1 billion.

Appalachian Power is a subsidiary of the American Electric Power Co., a giant, privately owned system that generates and distributes power from coal-fired, oil-fired, hydroelectric and nuclear plants in seven states. Energy Politics

AT LONG LAST, in short, the needs, interests and ambitions of industrial America have arrived on the doorstep of Poor Valley.

Which is why, improbably, this remote and tranquil vestige of 18th-century America is not a bad starting point for a look at the politics of energy in late 20th century America. That will be a society where there will be, for the foreseeable future, an overall shortage of energy: the United States, which was self-sufficient in energy until 1970, now imports close to half of its energy, mostly in the form of oil from the Persian Gulf. It will also almost certainly be a society that will have to adjust to lower levels of energy consumption than the power interests are planning.

The immediate politics are not very complicated. The hundred-odd property owners in Brumley Gap don't want their valley flooded. But they are neither rich nor radical nor particularly sophisticated. One of the handful of university-trained environmentalists who is trying to help them in their fight to save the valley says, "Just about the only thing you could organise these people against is the devil." A Coalition of Appalachian Energy Consumers has been formed. It includes the Mineworkers' Union and various national environmental groups. But there are limits to the interests shared between mountain people fighting for their homes and radicals or environmentalists battling the power interests on ideological grounds.

What's more, the people of Poor Valley are far outnumbered by the rest of the inhabitants of Washington County, who are somewhat tempted by the company's promise to create 800 to 1,200 temporary construction jobs, and even more tempted by the lower taxes they think they will have to pay once the county's tax base has been swollen by a billion dollars' worth of pump storage.

The APCO project has only begun to go through the rather lengthy process of getting official permission to build, whether at Brumley Gap or at Powell Mountain. The company has applied for a preliminary permit from the Federal Energy Regulatory Commission. Supposing APCO wins that round, it will still have to apply to the Interior Department in Washington; to the Virginia State Corporation Commission for permission to raise its electricity rates to pay for the project, and finally for a def nitive license from the FERC.

Each of these applications is in the public domain, so that the public, whether directly affected or not, has opportunities of learning about and of opposing such giant power projects, even though, in quasi-legal proceedings of this kind, the dice are heavily loaded in favor of big power companies that can afford to be represented by squadrons of expensive lawyers.

At the very least, in any case, it will be three years before the company is able to start moving earth, and probably far longer. And so far the lack of political interest on the state, let alone the federal, level is deafening. Only one of Virginia's congressmen has shown any interest whatever in what -- quite apart from the issues involved -- will be the biggest single hydroelectric project in the western hemisphere.

Yet larger issues are involved. For one thing, APCO admits that a pump storage facility, either at Brumley Gap or at Powell Mountain, would have to be tied into one of the new extra-high voltage (EHV) 765 kilovolt (kV) power transmission lines. Because transporting electric power at high voltages is more economical, especially because of the reduced amount of land that needs to be bought for right of way to transmit a given voltage, more and more of these EHV lines are likely to be built in the future, both in the United States and elsewhere. Indeed there is talk of building ultra-high-volt-age (UHV) lines to carry 1,000 kV and even higher voltages. American Electric Power pioneered extra-high-volt-age transmission and already operates the first 765 kV line to be built in the United States, in Ohio and adjacent states. But many more are planned, and opposition to them is building up. North Country Anger

THE PEOPLE WHO live in the vast tract of upper New York State above the Mohawk valley call it the North Country. It is chiefly occupied by the Adirondack mountains, and most of the skimpy population lives along the St. Lawrence River in the north, in an area of dairy farms, sugar maples and a few riverside industries. Canadian cities like Montreal and Ottawa are far nearer than the New York State capital at Albany, let alone "the City," as it is called with a mixture of fear and loathing. North Country people have a long history of feeling alternately ignored and exploited by both Albany and the City, and their feeling is by no means unjustified.

Now the inverted triangles of 765 kV line are beginning to snake across the North Country, and the traditional local resentements are boiling over. Last year, demonstrators went through the motions of offering their bodies to the chain saw -- in front of the cameras, of course -- when the felling crews moved in to start clearing the right of way for the line. There were more demonstrations when I was in the North Country in October.

One good reason for resisting the spread of 765 kV lines is that they may well be dangerous. No one knows how dangerous. There are no official safety standards in the United States governing the safe limits on the intensity of electromagnetic fields from EHV lines. The electric field from a 765 kV line 45 feet above the ground is strong enough to put a voltage into objects such as vehicles or fences that can give someone who touches them a nasty shock.

Even more worrying are the biological effects of the electrical and magnetic fields from 765 kV lines. Studies done in the Soviet Union suggest that people working with super-high voltages complained of headaches, irritability, fatigue, faulty memory, heart pains and sexual impotence.

Soviet transmission systems are differently and -- Americans believe -- less safely built than U.S. lines. But American researchers, too, have found what one of them has called "a solid body of data" indicating that living organisms are adversely affected by EHV fields. The effects can apparently include serious damage to human cardiovascular and central nervous systems. EHV lines also produce ozone in quantities that could harm animals, humans and growing crops, not to mention radio interference and noise.

That is bad enough. But the North Country opponents of 765 kV lines suspect that behind them lurks an even more obnoxious threat: nuclear power. There are already several nuclear power stations in New York State. But environmentalists in the North Country are afraid that, just because their part of New York State is an empty area between the great conurbations of New York, Boston, Buffalo and Montreal, the power companies, aided and abetted by state and local government, intend to turn it into a vast nuclear energy center for northeast North America.

A report by one journalist and environmental campaigner, Jackie Sharpe, finds that after Congress passed the Energy Reorganization Act in 1974, the Argonne National Laboratory proposed the St. Lawrence Valley as one of four alternative sites for such a nuclear energy center. She said the government report called for building no fewer than twelve 765 kV lines in six corridors, each 430 feet wide. Clash of Ideologies

THE SAME FEAR of nuclear power also underlies some of the opposition to the Brumley Gap or Powell Mountain pump storage projects in Virginia. Coal- or oil-operated generating plants may be inefficient on a peak basis, but it is possible to cool them down and use them to generate different levels of power at different times. Nuclear plants, on the other hand, cannot be operated on a peak basis at all. And so the opponents of nuclear power suspect that the ultimate rationale for building immensely expensive and relatively inefficient pump storage plants can only be an intention on the part of the power companies of going over to nuclear generation in a major way.

But behind the immediate clash of interests -- for example between the power companies and their customers in the cities on the one side, and the minorities who inhabit the unspoiled arcadias of North America on the other -- and behind even the serious environmental arguments, there lie yet more basic issues of political power and purpose.

In the past dozen years, many developments have thrown doubt on the desirability and the practicability of infinite economic growth. But nowhere is the argument more clearcut than in the case of energy. The power companies -- and the oil companies, the natural gas interests, the coal people and the formidable coalition of political and economic power they have built up between them -- see the energy crisis as mere shortage. Their response is to raise the price of energy, so that the United States will once again be self-sufficient in it, and the majestic march of economic growth can go on.

But as more and more farmers see high-voltage pylons sweeping across their land, and more and more mountain people face the flooding of their valleys for hydroelectric. plants, or their ravaging by stripmining, above all as more and more consumers face endlessly rising bills for every kind of fuel, this energy producers' philosophy is bound to come more and more sharply in conflict in the arena of practical politics with a new philosophy that cries halt.

This is already not only a clash of ideologies, but also an argument about matters of fact. The power companies say that the demand for energy will be such in the future that they must start building new generating plants right now to meet future demand. But conservationists project far lower demand curves. And they point out that the power companies have every interest in maximizing estimates of future demand, since the greater the supply, the greater the profit for suppliers working essentially on a cost-plus rate basis. Moreover, the power companies' rates, fixed all too often by compliant state (not federal) regulatory bodies, take account of construction costs for new generating and transmission facilities.

It would be premature to predict a major political rebellion against the power companies. Americans are so ideologically inclined that they will rebel against taxes paid to government long before they rebel against electricity rates charged by private companies. But they are not fools. And in the end the assumption, diligently spread by decades of prestige advertising and buttressed by massive political activity, that the interests of the consumer and those of the commercial producer are identical, is bound to come under increasingly sharp scrutiny.

It would also be wrong to generalize too widely from two specific controversies -- the battle over nuclear power in the New York North Country, and the case of the Virginia pump storage project -- even though these are two of the most important test cases to have come up so far. What can be said is that already these and similar projects have raised -- as well as important and difficult issues of law, and equity and environmental health -- new questions of power and politics.

The power companies say they do not want to base their policies on asking Americans to make "lifestyle changes." For those Americans who happen to live in Poor Valley or the North Country, of course, that policy itself will change and even destroy their lifestyle. But that affects only a few whom the power interests no doubt feel they can afford to ignore.

What is more to the point, because even the most powerful interests cannot afford to ignore it, is that the United States is entering an age of energy shortage -- if not absolutely, or even compared to Western Europe or Japan, yet certainly relative to the historic abundance of cheap energy in North America. In such a new period, American politics will be to a considerable extent the politics of energy.

What's more, those who want to understand how the United States is going to behave will have to learn to study those politics in places like Brumley Gap and in the St. Lawrence valley, as well as in Washington and in the Persian Gulf.