There was a “hole race” alongside the space race.

Project Mohole drilling operation, 1961

As the United States and the Soviet Union started competing for space supremacy in the mid-20th century, they were also racing in the opposite direction. Both countries wanted to dig the deepest hole, with the goal of reaching the Earth’s mantle in order to better understand the planet’s interior and also demonstrate technical prowess. A group of American scientists took a first stab at the deep hole in 1961 by drilling into a deep sea bed, where the Earth’s crust is thinner. The Soviet Union, after years of planning, started drilling a hole on the Kola Peninsula in the Arctic Circle in 1970. Eventually, the Germans launched their own effort in Bavaria in 1990.

Ultimately, nobody reached the Earth’s mantle. The Soviet Union still finished on top: Around 1989, after drilling the Kola Superdeep Borehole for about 20 years, the Soviets reached a depth of about 7.5 miles. The hole is only about 9 inches across, too small for a human being to fall in, but it was sealed up with a metal cap in 2008 anyway. It’s still the deepest human-made hole on Earth.

The United States made it 601 feet deep under 11,700 feet of water before funding was pulled in 1967, although the project helped launch a new era of ocean exploration and brought up some valuable geological samples. Germany drilled more than 5.5 miles, but the drill got too hot to continue — a lower temperature is one advantage the Soviet Union had in the Arctic Circle. All of these efforts helped pave the way for future scientific drilling projects, ushering in technology that is still used by the oil and gas industry.

By the Numbers

Did you know?

More than a million acres of swampland was drained to create the Missouri Bootheel.

Before 1914, the Missouri Bootheel, a little panhandle at the southeast corner of the state, was a massive, 1.65 million-acre swamp fed by the Missouri River. Then one of the biggest drainage projects in the world transformed the land into the agricultural center it is today. In the early 20th century, landowners, many of whom were logging companies that had cleared the swamp’s hardwood forests, organized a massively ambitious drainage district. The digging started in 1914 and lasted until 1928, during which workers ultimately dug 900 miles of ditches and built 304 miles of levees, which currently drain 1.2 million acres of land.

At the time, the environmental impact of swamps wasn’t as well understood as it is today, and while the farmland created by the project produces about a third of Missouri’s economic output, it did diminish the habitat for many wildlife species. Only around 84,000 acres of the original swamp remain today, and much of it is in conservation districts.