Black Thunder is one of the largest and most efficient coal mines in the US and on average produces more than 2 tons of coal per second, 24 hours a day, 365 days a year. During the life of the mine, 61,347 trains, or 6.9 million cars, have been loaded with coal. If those trains were linked, they would circle the equator nearly three times, Arch said.

The production milestone was achieved in early December, 25 years after the mine's first coal shipment on December 14, 1977. Today, Black Thunder produces more than 65 million tons of coal annually, enough coal to provide electricity to nearly 4.5 million American households.

"This is a significant milestone," said Paul Lang, president of Thunder Basin Coal Company and general manager of the Black Thunder mine.

"To the best of our knowledge, Black Thunder is the first coal mine in the nation, if not the world, to achieve this milestone. It's a credit to all our hardworking employees who worked diligently to make this happen. And, it's significant for our nation, who reaps the benefits of greater energy independence by tapping into America's largest energy resource."

According to Arch, the US has 250 billion tons of coal reserves, equaling about one-fourth of the world's total. The US has a greater share of the world's coal than Saudi Arabia does of the world's oil. In fact, America's coal reserves represent the largest energy resource within the borders of a single country. Black Thunder produces roughly the same amount of energy as a 600,000 barrel-per-day oil field. Arch provides the fuel for approximately 6% of the electricity generated in the United States.

Black Thunder is an award-winning operation, and its achievements include environmental and safety milestones, such as the Mine Safety and Health Administration's Sentinels of Safety award achieved for working the most employee-hours in 2001 without a lost-time incident.