The Powder River Basin coal field in northeast Wyoming is the largest coal producing region in the U.S.A., and demand for it's low sulphur coal is increasing. Output is shipped to all parts of the country by Burlington Northern Santa Fe and Union Pacific. Most loaded unit coal trains weigh in at about 15,000 tons. UP now assigns high-tech state-of-the-art locos to it's coal trains, but at the time of my visits the invasion of new General Motors' SD70MACs had still not completely displaced older power from BNSF's trains, and my favourites, the General Electric C30-7s, were still much in evidence. Of particular interest to me has been the former BN route from Donkey Creek to Alliance, where loaded eastbounds stop at Crawford to attach helper power on the rear before tackling the 13 mile climb over scenic Crawford Hill, which has a ruling gradient of 1 in 65. Speed is restricted to 20mph on the hill; most eastbounds struggle up at 15 mph.