Coal isn't a 20th century fuel, that is more natural gas and oil, it is a 19th century fuel that for a lot of reasons stayed around, more than a few of them political, and it basically is an inefficient technology whose mining and delivery system, not to mention how it operates as a fuel, whose time has passed. Converting coal to gas or to gasoline is possible (the gas lamps of the 19th century were lit by coal gas), but that is costly, and also is converting an ancient fuel to one only slightly less ancient. The reality is that coal is being pushed out of the marketplace both by market forces and people not wanting to live with the consequences of burning coal, things like acid rain for example, or the damage done to beautiful areas by coal mining, the slag piles, water pollution and so forth, not to mention what coal mining does to the people who do it.
There is no doubt significant coal hauling going on, CSX for example has significant revenue from coal, I suspect both BNSF and the Union Pacific have due to shipping coal to the west coast to be shipped to China, potential exposure. Railroads are subject to the market, like anyone else, and there is plenty to ship without coal. I don't think it will destroy the railroads, I don't think it will result in them cutting back on maintainence, rather I think it will result in them modifying their business model to reflect reality, which might mean they drop the number of trains they run, maybe drop routes entirely, but it isn't like coal was to let's say the C and O back in the day, it isn't.
I don't know how you figure that coal isn't a 20th century fuel? 
The use of coal was huge in the 1920's, 30's, and 40's. Still widely used in the 1950's as well. Use probably didn't really go into decline (at least in the east) until the 1960's. There was even a brief comeback in the 1970's as the price of oil skyrocketed.
Jim
Coal was a 19th century fuel in that it was came to prominence in the 19th century with the industrial revolution, it ran the trains, it powered a lot of manufacturing plants, it also was used in the steel mills. It likewise was used to power the first power plants as well. When I said it was a 19th century fuel, I meant that it was and is inferior to other forms of power, it requires those mining it to risk their lives, as a fuel source no matter how much they tried it is dirty, and it puts out a lot more CO2 and CO emissions then burning other fuels. In some ways, it is much like railroads switching over from steam engines to diesels, the steam engine was inherently a 19th century technology, whereas the internal combustion engine was the 20th (and on a diesel, combined with the electric traction motor, that was born around the turn of the 20th century).
It wasn't that coal wasn't heavily used, it has been, it still generates a lot of power, but in the 20th century coal has been in decline since oil and gasoline and later natural gas went on the rise. It had momentum, in large part because the power companies and the companies that used coal in manufacturing, like the steel industry, were going to get every cent out of their plants. Politically, big coal and their allies had a lot of clout, and rules and regulations allow coal to be used well after it should have been regulated, and before someone tell me how coal isn't that bad, take a look at China, their infamous pollution is mostly due to burning coal (not to mention that London's famous fog was not entirely natural, it was basically a perpetual fog of coal smoke). Lakes and rivers were dying off because of acid rain from sulfur, and the human cost from the pollution they put out is huge (and nicely dispersed from original source, those 500 foot tall smokestacks simply dispersed the pollution down the road several states over, talk about crapping on your neighbors).
There have been all kinds of attempts to push coal, we had the government spending literally billions on researching "clean coal", that basically ended up being a massive pr campaign with nothing to show for it, in the 1970's it was pushed as a way for the US to be energy independent, but in the end it turned out not to be practical (yes, you can make gas and gasoline out of coal, but it is very, very inefficient and costly compared to natural gas). Plus, the human cost in mining it is a big issue as well. Coal had a kind of rebirth when China industrialized, but even they realize they can't go on using it, they are choking themselves.
Fossil fuels themselves are in some ways dinosaurs, while natural gas is a lot cleaner than coal (and also in power plants is a lot more economically viable in the long run, gas fired power plants have longer lives and require less maintenance) , and modern gasoline engines burn a 1000 times cleaner than they once did, it is still technologically obsolete, and eventually it too will be replaced, either by biologically generated gas and oil products, rather than burning stuff laid down millions of years ago that is not ecologically balanced, or by other kinds of energy sources, it is the nature of change, and coal is at the bottom of that heap. Romaticizing coal is like romanticizing 19th century railroading, both were needed advancements for their time, but there was little romantic about it.
