But the Soviets were trying to reach a depth of about 49,000 feet below the Earth’s surface using specialized equipment. They started to dig a series of holes all branching off from a single main cavity. But while they were slowly getting there, the US also made progress of their own. In 1974, the Lone Star Producing Company started to drill for oil in Washita County, western Oklahoma. In the process, the company created the Bertha Rogers Hole, a man-made wonder that reached more than 31,400 feet, or nearly six miles, below the earth’s surface.
