Belle Ayr, in the prairies of Wyoming, is one of America's major coal producers. It's an extremely busy mine with a lot of activity on the haul roads where the 380-ton Cat 797B is king. But even this is dwarfed by its loaders among which are four classes of electric shovels including two monsters: the P&H 4100XPB and Bucyrus 495HR, both with 82 cu yd dippers. This mine is one of a number which provide coal for the eastern power stations, shipped by trains over a mile long. The DVD includes the filling of some of these 100-ton rail cars. By contrast, Beener Coal in Maryland is typical of the smaller mines that operate in the Appalachians. Here they use diesel power rather than electricity. The two stars are the world's largest bulldozer, the Komatsu D575A, working alongside the world's largest diesel shovel, the Bucyrus-Erie 295B series 2.