Coal has been part of America's past for just about as long as there's been an America.
It was the energy source du jour for the Industrial Revolution. In the 1300s, some Native Americans used it for cooking fuel. And the first North American coal deposits may even predate the dinosaurs!
But if we're talking America the post-colonial country, then nowhere was it more important than in the Appalachian Mountains, in places like Pennsylvania, Kentucky, Tennessee, and West Virginia.
Unfortunately, what coal mining looked like back then and what coal mining looks like now are stunningly different. According a new study, coal mining is actually changing the entire landscape of Appalachia.
So let's jump in the Wayback Machine to 1930s Appalachia and see what things were like (and how things have changed for the better and worse) in 18 pictures:
1. Everyone looked dapper as hell back in 1935.
Sunday, 1935. Image from The New York Public Library.
2. Including this ridiculously photogenic schoolteacher.
Schoolteacher in Red House, West Virginia, 1935. Image from The New York Public Library.
3. Who may have actually taught in this somewhat photogenic classroom.
School in Red House, 1935. Image from The New York Public Library.
4. Check out the awesome kid in the front. Respect.
Schoolchildren of Omar, West Virginia. Date unknown. Image from The New York Public Library.
Unfortunately, the kids in this picture and the one above it probably wouldn't have been seen in the same classroom. Segregation was still very much a thing in the '30s, which meant that many public spaces, including schools, were divided by race. Things would largely remain this way until the mid-1960s.
5. Outside of school and work, people went to the movies – which cost a dime.
Movie theater in Omar, 1935. Image from The New York Public Library.
6. They entertained themselves by playing music.
Musicians in Maynardville, Tennessee, 1935. Image from Ben Shahn/Wikimedia Commons.
Appalachia is home to some of America's richest musical traditions, including country and bluegrass.
7. They even "pirated" football games.
Men watching football in Star City, West Virginia, 1935. Image from The New York Public Library.
If by "pirated" you mean "watched through a fence while nobody was looking."
8. This is Williamson, West Virginia, in 1935.
Image from The New York Pubic Library.
It's changed a lot since then.
9. This is Williamson in 2008.
Image from Flo Night/Wikimedia Commons.
Williamson is home to the Williamson Rail Yard, which serviced the many coal mines in the region.
10. Coal miners worked long hours in dark, dangerous mines.
Coal miners in Kentucky, 1935. Image from The New York Public Library.
11. Coal mining was tough, dangerous work.
Slate pickers separating the coal from rock in Scranton, Pennsylvania. Date unknown. Image from The New York Public Library.
Coal mining required workers to do backbreaking labor in cramped conditions, often deep underground.
12. But it was honorable work and, for many people, the best way to provide for their families.
A coal miner with his family in 1938. Image from The New York Public Library.
13. As much respect as we have for coal miners of the past, it can be hard to support the industry today. Because in 1935, coal mining looked like this:
Image from The New York Public Library.
14. But now, coal mining looks like this:
GIF from Smithsonian Channel/YouTube.
See how flat that is? A lot of modern coal companies use a technique known as mountaintop removal mining to get at the remaining coal seams tucked deep into the mountains.
15. Mountaintop removal mining is exactly what it sounds like: blasting away the entire top of a mountain to get to the coal below.
Image from ilovemountains.org/Flickr.
This practice is widespread throughout coal country. In fact, a new study found that the area of study became 40% flatter after mountaintop removal mining. This has a lot of people worried about the effects on the geology and ecosystems in the area.
"Even if we stopped mountaintop mining tomorrow, what kind of landscape is going to be left behind?" said study author Emily S. Bernhardt.
16. Even more worrisome is what mountaintop removal mining may be doing to the water.
Image from ilovemountains.org/Flickr.
Excess rock and refuse often ends up dumped in gigantic piles in the valleys and streams below the mountain. Heavy metals and chemicals can leach out of the pile into the waterway, affecting any animals or people downstream.
17. The hardworking men and women who've done this job for generations deserve respect. But ... there's a better way.
Coal is an intimate part of Appalachia's history and the last thing we want to do is claim that it's not important. But Appalachia has a long history of renewables too. They've had hydroelectric power plants for over 100 years!
A wind farm in Somerset, Pennsylvania. Image from Jeff Kubina/Flickr.
Even though coal production has been falling in the last few years, many coal companies are indicating that they want to double down on mountaintop removal mining.
But now that we know how harmful coal mining can be for the environment and have the technology and wherewithal to do something different, we can and should be looking elsewhere for our electricity.
18. Then maybe, just maybe, we can leave the dangerous job of coal mining and its effects on the environment where they belong: in the past.
Coal miners in Williamson, 1935. Image from The New York Public Library.
These matching bunny ears though. 
Many adult twins regret that their names are so closely linked together.