What happened to the abandoned coal mines in Pittsburgh? As part of 90.5 WESA's series Good Question, we look into the history of coal mining in the city.

When Emily Eckel moved to Knoxville, a neighborhood south of downtown Pittsburgh, she was told to buy special subsidence insurance, just in case the abandoned coal mine beneath her house ever caved in. She'd never heard of it.

“I just started imagining this vast maze of coal mines under the city," she said. "I was picturing coal miners going in with a pickaxe or a shovel and a yellow canary and a cage and mining all day. I don’t know if it was like that, and I would like to know.”

It was not exactly like that, at least not in Pittsburgh.

“Look, if you didn’t have coal, America wouldn’t have (had) squat,” said historian and author Carmen DiCiccio. “It fueled industrial America.”

He penned “Coal and Coke in Pennsylvania,” described as “an authoritative overview and best single source on the history of Pennsylvania’s bituminous coal and coke industry,” for the Pennsylvania Historical and Museum Commission in 1996.

Pennsylvania is credited with almost one-third of America's abandoned mines, DiCiccio said, and most of those are in the southwestern portion of the commonwealth. In the early establishment of the city of Pittsburgh at Fort Pitt, soldiers relied on the mineral deposit.

Maps as early as 1761 note a “coal pit” on what became Mt. Washington. For decades, the neighborhood was known as Coal Hill.

James Kenny was a young Quaker merchant who lived at Fort Pitt from 1759 to 1763. Michael Burke, a curator at the Fort Pitt Museum, described Kenny as a naturalist who noted the features of the area in his personal journals.

“I and my brother and two other men went to see the coal pit in land on the mountainside over the Monongahela,” Kenny wrote in 1761. “The mountain is so high and so steep that it’s with care and difficulty people gets up to it. But it’s easy as the bank of it being dug away a piece.”

At the time, wood was the universal fuel, but what is now Downtown had been deforested to build Fort Pitt. There was an abundance of coal across the river, so instead of the time-consuming, labor-intensive work of cutting trees, soldiers scaled Coal Hill. Men like Kenny stuffed their sacks and rolled them down the hill to a docked boat on the Monongahela.

DiCiccio said it wasn’t just the abundance that swayed soldiers.

In 1796, the French government sent engineer Victor Collot to survey and map the area. He wrote, “(Coal) quality is equal to the best kind in England.”

But while Pittsburgh sat on a bed of quality fuel, there was no way to easily transport it.

Its main use for many years was to heat local homes.

An article in an 1814 edition of Zadock Cramer’s “The Navigator,” a guidebook for traveling the Monongahela and Ohio Rivers, said there were about 40 to 50 open horizontal pits. Most of mining in Pittsburgh was still visible from the surface and not very deep.

“Fuel, that indispensable necessary of life, is so cheap here that the poorest rarely suffer for the want of it,” Cramer wrote.

He also noted that the smoke from burning coal hung low over the city and that “even snow can scarcely be called white in Pittsburgh.”

See if your home is at risk for mine subsidence here.

In the late 1840s, railroad lines came to the region and the coal industry took off in Westmoreland, Greene and Fayette counties.

In Pittsburgh, mining continued at surface level. It wasn’t Eckel's image of sending hulking men with shovels hundreds of feet under the earth. Instead, they often dug out the side of a hill.

“They’re not miners, they’re farmers,” DiCiccio said. “I’ve been to sites where it’s sitting right there and you can take a pick shovel to it.”

The high-quality coal being mined outside of the city was baked into a product called coke, which was used in the production of Pittsburgh steel.

“When you’re producing enough steel to build the Brooklyn Bridge, that’s some serious steel, which means some serious coke, which means some serious coal,” DiCiccio said.

He attributes the end of local coal mining to a lethal combination of the Great Depression and the invention of the continuous miner, a machine that did the job of three men.

By the 1930s, most mines in Pittsburgh were gone or long since buried by newer property, but a few remain. The state Department of Environmental Protection estimates 60 abandoned mines are still within city limits, stretching through large swaths of the South Hills, Squirrel Hill and Stanton Heights.

They aren't benign neighbors.

The DEP estimates 230,000 homes in Allegheny County -- roughly 42,000 in Pittsburgh alone -- are at risk of sinking into the ground from subsidence, the term for a shift in the ground when a mine collapses.

It can cause gaping sinkholes, but is much more likely to lead to cracks in homeowners' foundations.

"A lot of people don't realize just how much infrastructure is beneath us," said Rick Schweikert, a licensed realtor with Keller Williams Realty who does most of his business in Pittsburgh's urban core.

Carl Massini, an engineer with the DEP’s Department of Mine Subsidence, said it's an unpredictable science. His office worked to stabilize an abandoned mine in Mt. Oliver in 2013 when the department determined 20 homes had been damaged from subsidence.

“It’s a very sudden occurrence where you get a collapse to the mine, and if that propagates up to the surface, it’s kind of overnight that the problem occurs,” he said.

Even shallow mines in Pittsburgh could damage a basement or foundation, he said. The department offers subsidence insurance, but Massini estimates only about 10 percent of homes at risk carry it.

Schweikert said he's seen structural problems in several homes around Squirrel Hill and Stanton Heights but never heard anyone definitively attribute those issues to mine subsidence.

Some homes are old, poorly designed for water drainage or built with materials that degrade over time, he said. A lot of his clients have gotten riders exempting them from insurance.

"People ask about steel or why it is that the coal rights were transferred more than 100 years ago," Schweikert said. "They want to hear the history; they aren't concerned about mines."

What have you always wondered about the Pittsburgh region? Submit to our Good Question! series and we’ll go investigate and find answers.