Bertha Rodgers
In western Oklahoma, the Lone Star Producing Company reached a depth of 9.5 kilometers in its search for oil. Unfortunately, the company did not find what they were looking for during their drilling operations in 1974: not a single drop of oil was found in this place. The so-called Bertha Rodgers hole remained the deepest bore in the world for the next five years.
This record was broken on June 6, 1979 by the Soviet-funded Kola borehole. Four years later, in 1983, the hole even reached a dizzying depth of 11.9 kilometers. To give you an idea of what this looked like: The diameter of the hole was only six inches.