TOWANDA, Pa. — Ever since President Nixon's 1973 promise to attain energy independence, every successive president has pledged the same goal, even as foreign supplies composed a larger and larger share of the U.S. energy mix.

A measure of independence now is within reach even though, as this booming mountain town in northeastern Pennsylvania shows, the quest involves both opportunities and trade-offs.

It may surprise Americans who have lived through years of dependence on foreign fuels, but the United States could pass its 1970s peak as an oil-and-gas producer in less than a decade. If that happens — and many analysts believe it's possible — the nation would edge past Saudi Arabia and Russia to become the world's top energy producer.

That alone wouldn't make us completely energy independent. Mexico and Canada are likely to remain stable providers of oil to supplement growing U.S. production. Other factors will help, too, ranging from advances in battery technologies and alternative fuels such as ethanol to greater fuel economy in automobiles.

However, the biggest potential game changer for U.S. energy production is natural gas, previously supplied largely from the Gulf of Mexico region. Not long ago, terminals were being built at U.S. ports in anticipation of importing natural gas; today, there's talk of exporting it.

Technological advances have allowed drillers to go down almost 7,000 feet, smashing through rock formations and drilling horizontally, freeing trapped oil and gas long considered inaccessible.

"Shale gas, the biggest energy innovation since the start of the new century, has turned what was an imminent shortage in the United States into what may be a hundred-year supply and may do the same elsewhere in the world," Daniel Yergin, the world's most prominent oil historian, wrote in his new book about energy security, "The Quest."

Bradford County

The promise of shale gas is present in many places, but it's nowhere more visible than in northeastern Pennsylvania's Bradford County, in the aptly named Endless Mountains region. Hundreds of communities sit atop the Marcellus Shale formation, which runs along southern New York through western Pennsylvania into eastern Ohio and parts of Maryland and West Virginia.

Geologists believe the formation contains the second-largest natural-gas deposits in the world, behind only Iran's South Pars-North Dome gas field in the Persian Gulf, off the coasts of Iran and Qatar.

If America becomes energy independent, it will be, in large part, thanks to the Marcellus Shale region. Energy consultancy PFC Energy projects the United States will recapture the flag of top energy producer within eight years.

"We need to continue to have increased drilling and production. It looks like the resource base is there to support that. The evidence is there for that; I think it's a pretty high probability," said Bob MacKnight, a PFC senior manager, who added that large U.S.-based energy companies are "rediscovering" the United States. "A lot of these companies had left the U.S. for dead 10 years ago and are now realizing the type of growth they can get here onshore is a scale they didn't think existed."

Onshore is the operative word. Offshore drilling has brought new oil resources, and new ultra-deepwater production was replacing lost conventional domestic supplies and beginning to reduce the amount of imported oil before the April 2010 BP oil spill. The federal government on Dec. 14 unsealed the winning bids on the first deepwater leases since the devastating spill, showing there's still strong interest in deepwater drilling.

But oil and gas from shale is the biggest new phenomenon.

"To have energy independence, you need to have energy," said Brian Grove, director of corporate relations in Towanda for Chesapeake Energy, the most active player in Pennsylvania's Endless Mountains region. "We've grown our production here from zero to hundreds of millions of cubic feet per day. ... It's going to take decades for development."

Lower prices

Utilities are expected to be the largest beneficiaries of the new production, and that's likely to translate into cheaper electricity for companies and consumers alike. Already, there have been a number of high-profile announcements of new Northeast power plants in the Northeast that won't need oil or coal to operate.

Forecaster IHS Global Insight projects the abundant supply will lower natural-gas prices, reduce electricity costs by an average of 10 percent nationwide and boost industrial production by 2.9 percent by 2017, as manufacturers enjoy cost savings. Natural gas also is likely to displace a lot of heating oil in the Northeast.

Demand remains a limitation. Manufacturers are big users of natural gas, and some cities have switched public buses to natural gas. But the scale of demand has yet to approach the available supplies, and producers want a more active federal policy that encourages the wider use of natural gas.

"We've got a supply of natural gas. We need an energy policy that reflects that," said Kristi Gittins, vice president of industry and public affairs for Chief Oil & Gas, a Dallas-based driller that's drilled more than 150 wells along the Marcellus Shale formation and has three that now are operational.

Shale-gas production now accounts for anywhere from 23 to 34 percent of U.S. marketed production, according to differing estimates by energy consultants. That will grow to at least 42 percent by 2020, PFC Energy said. IHS Global Insight projects it will grow to 60 percent by 2035.

Environmental concerns are one potential brake on the shale boom. There are worries about risks to water tables from hydraulic fracturing, the fancy name for shooting pressurized water, sand and chemicals deep into the ground to ease shale gas to the surface. Industry says the process is safe, but the Environmental Protection Agency this month linked chemicals in the groundwater of a small Wyoming town to hydraulic fracturing, also known as fracking.

Bradford County residents, including Wyalusing volunteer fire chief Adam Dietz, share many of those concerns, but some consider it a chance they're willing to take.

"Forty years from now we might look back and say, 'What the hell did we do?' Or maybe not. Life's a gamble," he said.