Author: Jason Smith
As a new resident of Arizona, I’ve spent some time scrolling through aerial imagery of the surrounding landscape, examining the evolution of cities like Phoenix, Tempe, and Mesa over the decades. This week, I spotted something I hadn't seen before—a large circular track etched into the desert floor, flanked by smaller ovals, long narrow loops, and serpentine courses.
I’ve written about racetracks before—this was something different. The patterns were very specifically engineered, and not necessarily for speed. The newest imagery of the site showed its recent transformation into a planned suburban community, but the older aerials revealed a very intriguing past.
https://www.youtube.com/shorts/-xgYiRwnY_U
Some of you probably knew what it was right away. After a quick search, I learned that what I saw was the General Motors Desert Proving Ground. This was a massive facility where engineers tested cars against the desert’s extremes.
Of course, I knew that automotive testing happens all the time, of course, but I’d never really thought about where or how it was done until now. We all know the crash test dummies—those stoic icons of safety that we’ve seen in commercials and public safety advisories. But I bet that few people think about the places where entire fleets of vehicles are pushed to failure, rebuilt, and tested again.
These sites are highly secretive and surveilled, but aerial imagery gives us an idea of the variety and extent of testing that goes on. My discovery in Mesa sparked questions: when did automakers start building these secret kingdoms of speed and science? Where are the rest of them?
Here’s what I learned about automotive proving grounds and some of the most significant facilities:
In the earliest years of motoring, testing happened on public roads—dusty, uneven, and unpredictable. Engineers rattled through the countryside, jotting notes about failures and fixes. As cars grew faster and more complex, this method became unsustainable. Speed demanded safety, and safety demanded control. By the 1920s, the first dedicated proving grounds emerged, designed to simulate everything from cobblestone streets to mountain passes.
The pioneer was General Motors’ Milford Proving Ground, opened in 1924 in Michigan—their 100-year anniversary was celebrated last year. Spanning more than 4,000 acres, Milford became a living experiment in terrain and texture. There were steep grades, gravel pits, cobbled lanes, and rutted dirt tracks designed to replicate the harshest conditions. The centerpiece of this site is “’Black Lake’… a 67-acre test pad (equivalent to 51 football fields) used for dynamic vehicle testing in different weather conditions.”
[1967 and 2022 aerial views of the Milford Proving Ground - Milford, Michigan. Source: HistoricAerials.com](https://cdn.knightlab.com/libs/juxtapose/latest/embed/index.html?uid=c03dda40-c0b6-11f0-ba1b-0e6f42328d7d&width=100%&height=680)
1967 and 2022 aerial views of the Milford Proving Ground - Milford, Michigan. Source: HistoricAerials.com
Milford is where “cars go to find their breaking point.” Yet it wasn’t destruction for its own sake. It was refinement by fire. Over the decades, test drivers there endured Michigan’s bitter winters and humid summers to tune everything from Cadillac suspensions to Chevrolet truck frames.
Milford was also the site for the development of a wide variety of safety features. It hosted the first vehicle rollover tests in 1934, as well as the development of the first guardrails. GM also developed the “infant love seat” at Milford, which was used as a model for future child car seats.
A year after GM opened its Milford facility, Ford followed suit, opening the Dearborn Proving Ground in 1925 on the site of what had been southeast Michigan’s first airport. Built beside Henry Ford’s River Rouge industrial complex, it was symbolic: cars were born at the Rouge and tested next door. The oval track and endurance loops were modest by today’s standards, but revolutionary at the time. Engineers there went beyond just testing cars—they tested the public’s confidence in them.
[1951 and 2022 aerial views of the Ford Proving Ground in Dearborn, Michigan. Source: HistoricAerials.com](https://cdn.knightlab.com/libs/juxtapose/latest/embed/index.html?uid=49e4f310-c0b6-11f0-ba1b-0e6f42328d7d&width=100%&height=680)
1951 and 2022 aerial views of the Ford Proving Ground in Dearborn, Michigan. Source: HistoricAerials.com
Early Ford advertising proudly declared that its vehicles had “been tested on the Ford track,” a reassurance to buyers still wary of mechanical breakdowns on America’s rough, unpaved roads. Engineers pushed the Model T and its successors to failure points to improve reliability. One often-repeated anecdote describes engineers driving nonstop for 10,000 miles around the oval, pausing only for fuel and tire changes. This was a feat of endurance for both man and machine.
As vehicles evolved, Dearborn’s space grew cramped. By the 1950s, Ford had built their Arizona Proving Ground near Yucca, expanding into harsher climates. Still, Dearborn’s track remained the birthplace of Ford’s reputation for durability, where even the smallest squeak or rattle was treated like a personal insult.