Among the issues on which Chicago and Downstate disagree, coal is one of the more significant. In Chicago, it's seen as a relic of 20th Century industrialism, destined to be replaced by cleaner sources of energy like natural gas or wind power. In Southern Illinois, coal remains the rock on which the local economy is built. Coal mining is the best paying job in town, with experienced miners earning six figures a year.

So significant is coal's place in Southern Illinois history that earlier this month, West Frankfort hosted its annual Old King Coal Festival, an event whose sentiment is best summed up by the t-shirts for sale on its midway:

West Frankfort is the site of one of the worst mining disasters in American history. In 1951, an explosion at the Orient #2 mine killed 119 workers. The Orient disaster inspired the Federal Coal Mine Safety Act, which requires annual mine inspections and gives the government the power to shut down unsafe operations. A granite pyramid in the town's Coal Miners Memorial Park honors the fallen:

"THOSE WHO LOST THEIR LIVES WITHIN THE EARTH BELOW! WE HONOR 'YOU' WHO BLAST AND DIG AND LOAD OUR RESOURCE…'COAL'!"

I was at last year's Old King Coal Festival. It resembled most small-town civic pride weekends: a midway selling cotton candy and offering rides on the Jungle Twist; a country music stage, headlined by Nashville singer Ronnie McDowell, best known for his Elvis tribute "The King Is Gone"; a parade through the four blocks of the Coolidge-era downtown, with fire trucks, ambulances, the Carbondale High School marching band, and even Old King Coal himself, a retired miner riding in a convertible Corvette.

The only difference between the Old King Coal Festival and, say, the Warrensburg Corn Festival, was that it celebrated a product whose future is a matter of political controversy.

When the festival was founded in 1941, coal was still mined with picks and shovels, a laborious process that required the work of 50,000 miners in Illinois. Today, coal is extracted with automated longwall machinery that strips the rock off the mine wall. Illinois still produces about the same amount of coal as it did in the 1950s and '60s — 48 million tons — but longwall mining is so efficient that it only takes 3,000 miners, a fraction of Southern Illinois's workforce.

Despite its shrinking role in the state’s economy, coal is still a huge political issue in Illinois. Back in 2011, Gov. Pat Quinn was ready to appoint 49th Ward Ald. Joe Moore as director of the Illinois EPA. But Moore's nomination was opposed by business groups who didn't appreciate his sponsorship of Chicago's Clean Power Ordinance. (Moore also played a role in closing the Fisk and Crawford power plants in 2012.)

In the 2016 election, Southern Illinois voted overwhelmingly for Donald Trump, who campaigned on a platform of putting coal miners back to work. When Barack Obama was president, coal production declined 40 percent nationwide. Natural gas surpassed coal as the nation's leading energy source, producing 34 percent of power versus coal's all-time low of 30 percent. Trump ended Obama's Clean Power Plan and Stream Protection Act and withdrew from the Paris Climate Accords. In 2017, Illinois coal production increased 10 percent.

(Elected on Trump's coattails were Sen. Dale Fowler and state Rep. Dave Severin, basically ending the Democratic Party's historic dominance of Southern Illinois. During the Miners' Memorial Service at last year's Old King Coal Festival, Severin told the crowd that when he leaves Springfield for a trip home, he tells his colleagues, "I'm going to God's Country, where it's God, guns, and coal. I even tell that to the people from Chicago, where they can't even spell 'coal.'")

In general, the coal miners I met in West Frankfort were:

• Big fans of Trump, because he was standing up for their industry
• Grateful to be earning more than $100,000 a year in a town where the median home price is $87,000
• Reluctant to have their children becoming miners, because they don't think coal has a future.

"I honestly think that if the election had gone the other way, it would have been lights out for the coal industry," said Josh Owens, a miner I met at the festival. "It was on its knees at the end of the Obama Administration."

Owens had worked lower-paying jobs at a tire factory, nail factory, and bottling plant before catching on in the mines. When I talked to him, he was preparing to fly to New York City for a weekend of sightseeing.

"Not too many people in this area can afford to do that," he said.

Then there was Dusty Melvin, who came back to West Frankfort after leaving the Marine Corps in 2001. Looking for a job that would allow him to raise a family in his hometown, he asked his coal miner father to get him an interview.

"I'll get you one," his dad said, "but you're not going to like it."

Melvin got the job, and he likes it. As a longwall coordinator in the Mach Mine, north of Thompsonville, he supervises 160 men who operate the machines that claw coal from the mine walls. He's proud of mining a resource that heats America's homes and forges its steel.

"Every industry in America comes out of agriculture or coal mining," he said.

The Mach Mine generates 55,000 tons of raw coal a day, and sits on 40 years of reserves, more than enough to carry Melvin to retirement. After that, though:

"Coal mining is a hard living, man," said Melvin, who usually spends 50 or 60 hours a week underground, and doesn't want the same for his four sons. "My kids are gonna go to school; they're gonna move out. For a kid that's 15, who wants to work 'til 60 and retire, I don't think it'll happen. Technology will result in a cheaper form of energy."

This corner of the state is already over coal. In the Chicago area, the only remaining coal-fired plants are in Romeoville and Waukegan. In Joliet, a plant was recently converted from coal to natural gas.

In Southern Illinois, though, citizens and politicians will fight to keep coal burning until the last kilowatt is extracted from the last black rock in the earth.