Under pressure from the Sierra Club and federal and state government agencies, five power plants in Iowa will phase out the use of coal, putting the Sierra Club that much closer to forcing the closure of half the nation’s 523 coal-fired plants by 2017.

A federal district court settlement between the Department of Justice, the Environmental Protection Agency, the Sierra Club, and Iowa state agencies will force Interstate Power and Light to either switch from coal to natural gas or to shutter entirely five plants in the state. Two other power plants will get new pollution controls, according to an article at Huffington Post.

With the five latest power plants in Iowa, the Sierra Club has now had a hand in closing a total of 200 coal-fired plants under its “Beyond Coal” campaign. When the effort was launched six years ago, the Sierra Club said it hoped to see half the country’s coal plants shut by 2020. Now that date has been moved forward.

Interstate Power and Light also has agreed to spend $6 million on environmental mitigation projects and pay $1.1 million for Clean Air Act violations, Huffington Post reported.

“Back in 2009, the prevailing wisdom was that coal was inevitable, that the U.S. would be burning coal for a long time,” Bruce Nilles, ‎senior campaign director for Beyond Coal, said. “We set out to show that you can make a lot of progress even without a climate bill.”

Alliant Energy, the Interstate subsidiary that operates the plants, said that it, too, was pleased with the settlement.

Coal is in sharp decline

Coal as been the largest fuel source for generating electricity in the U.S. for more than 60 years, but its share of total net generation dropped from about 50% in 2007 to 39% in 2013, according to the U.S. Energy Information Administration. Almost all of the coal consumed in the U.S., 93%, is used for generating electricity. It added up to more than 858 million short tons in 2013.

Cheap natural gas is one reason that coal use is on the decline. The Obama administration’s Clean Power Plan, which seeks a 30% reduction in carbon emissions over 2005 levels by 2030, also is likely to mean more closures.

Mining interests don’t like it, but the Environmental Protection Agency says that in addition to cleaner air, the plan will lower power bills by roughly 8% by 2030.

Mary Anne Hitt, director of the Beyond Coal campaign, told the Huffington Post that Iowa was an “appropriate place” to mark the closure of the 200th coal plant. With 5,708 megawatts of installed capacity, Iowa now generates more than 28% of its electricity from wind, according to the American Wind Energy Association, the highest percentage in the country.

“Iowa really is showing the rest of the country what their economy can look like,” Hitt said, “[and] how to do well and prosper in a world powered by more and more clean energy.”

Politico says that Beyond Coal, with the deep pockets of Michael Bloomberg behind it, is “the most extensive, expensive and effective campaign in the club’s 123-year history, and maybe the history of the environmental movement.”

The coal industry, the report notes, now employs fewer people than the solar industry.