On 20 July 1969, the world paused as an estimated 600 million people watched Neil Armstrong and Buzz Aldrin walk on the moon. But few knew they were watching steps those men had long practiced in the canyons, craters and lava fields of Arizona.

Fifty years after the moon landing, Arizona’s role remains a forgotten piece of history – but this pockmarked landscape of high rocky plains once served as Nasa’s training ground for astronauts headed to the lunar surface.

The Apollo 11 mission prepared for its groundbreaking voyage outside Flagstaff, a small city nestled in a forest of ponderosa pines at the base of the San Francisco Peaks, Arizona’s tallest mountains. In fact, all 24 astronauts who have ever flown to the moon trained here. As the home of the famous Lowell Observatory, credited with discovering the planet Pluto in 1930, Flagstaff has an illustrious space history. But it took center stage during the 1960s space race when Nasa began its hunt for a moon stand-in.

The US space agency needed a geologically diverse landscape, one ragged and raw, torn and pummeled, and still bearing distinctive scars from a rowdy past. Flagstaff was made to order. The San Francisco Peaks are actually the remains of a hulking stratovolcano. The town sits amid the San Francisco volcanic field, dotted with hundreds of craters, cones and vents.

Scientists thought the volcanic cinders of the terrain might be similar to what astronauts would find on the moon. Additionally, the nearby Meteor Crater, the best-preserved impact crater on earth, and the great cosmic gash of Grand Canyon, provided an unmatched geological classroom.

Between January 1963 and November 1972, scientists based in Flagstaff would lead 200 separate geological field-training exercises for Nasa’s astronauts.

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The astronauts spent their time learning how to identify defining geological features they might encounter on the moon, how to collect samples and gather data. They tested the tools they would be using, and versions of spacesuits (modifications had to be made on some of the early suits because they did not fare well around the volcanic rocks).

They also began testing lunar rovers that would be used in later Apollo missions. “The early astronauts were all test pilot jocks,” explains Kevin Schindler, a historian at the Lowell Observatory. “Their focus was on flying and the challenges they might have to overcome. And this setting was also ideal for training and testing equipment.”

Facebook Twitter Pinterest Joe O’Connor testing a spacesuit at Hopi Buttes Volcanic Field north-east of Flagstaff, 1965. Photograph: USGS photo P45, F96547c

One of their early field trips was a long arduous hike to the bottom of the Grand Canyon. Accompanied by geologists, the two-day outing gave the astronauts a chance to learn how to identify different strata, detect faulting, see the impact of erosion and learn geological map reading.

Another important area of study was Meteor Crater. About 40 miles east of Flagstaff, the crater is gouged from the high plains, a bowl-shaped cavity nearly a mile across and more than 550 feet deep. There’s been some slight erosion and the bottom has partly filled in, but essentially the big hole hasn’t changed much in 50,000 years. Studying the formation helped prepare the astronauts to identify impact craters they would encounter on the moon.

Eventually, though, in 1967 Nasa decided to bring the moon to Flagstaff – or at least a simulation – by blasting craters of their own. Working with the Astrogeology Science Center, a division of the US Geological Survey established in Flagstaff to study solid bodies in the solar system, explosives were used to blow hundreds of craters in the volcanic terrain north of town.

The Cinder Lake Crater Field, as the artificial crater field was called, was designed to mimic Mare Tranquillitatis, the future landing site of Apollo 11. Here the astronauts tested spacesuits and equipment, practiced soil sampling techniques, honed lunar rover driving skills and prepared for lunar landings.

Their presence no doubt sparked some rather curious encounters at the tail end of the 60s. Imagine the poor students from Flagstaff’s Northern Arizona University communing with nature, or hikers exploring a distant trail, suddenly stumbling upon men in spacesuits driving what appeared to be a tricked-out dune buggy across cinder hills.

Fifty years later, evidence of the period is still visible. Cinder Lake Crater Field remains, although it has been degraded by the elements and human use, and is now a popular site for off-roaders and ATVs. Two lunar rovers were built in Flagstaff, and one – Grover the Rover – is still on display at the Astrogeology Science Center, where their space exploration work continues.

“The scientists continue to work with astronauts providing the essential background in geology they’ll need for their missions,” said Schindler. “In fact, a group of astronauts will be arriving later this year to do fieldwork at some of the same places where the Apollo astronauts trained all those years ago.”

Schindler is proud of the role Arizona played in one of history’s defining events, one he says brought us closer together. “For at least a moment we stood not as Americans or Russians, males or females, black or white, but as human beings, watching our species pursue – and achieve – excellence,” he said. “Walking on the moon demonstrated what we can achieve when we work together on a common goal.”