One of the last working coal mines in southern Colorado is laying off miners because they have a large stock of unsold coal.
A hundred years ago, there were coal mines all up and down what is now the I-25 corridor, from north of Longmont south to Trinidad (and into New Mexico as well).
Most of the coal was used locally, for heating and industry. The former use mostly went away, while the later shrank, leaving power plants as the main customers.
Now the trend is away from coal — natural gas produces as much electricity as coal and is trending up. Burning gas produces fewer carbon emissions, although it's still fossil fuel, of course.
I don't think that anyone wants to go back to the smoky days when every household furnace was burning coal. But when I lived in a quiet older neighborhood of Cañon City, I used to walk out on a winter night and get a quick acrid whiff of coal smoke. Some of the neighbors never had upgraded.
That part of the town often seemed stopped in time, perhaps around 1950. Example: the Italian restaurant that still displayed a large photo of President Harry Truman on its dining room wall.