This 100-Year-Old Michigan 'City' Has Free Gas and No License Plates: Why Almost Nobody Can Enter

Four thousand acres of Michigan. An electrical substation, a wastewater plant, fire crews, and a medical centre that never shuts. No number plates on the cars. And, of roughly 81,000 salaried employees at the company that owns the place, fewer than 200 are cleared to drive its fastest roads.

The site is General Motors' Milford Proving Ground, which opened on 25 September 1924 and is the oldest dedicated vehicle testing facility in the world. It sits in suburban Michigan between GM's hubs in Flint, Detroit, Lansing, and Pontiac. GM describes it as rarely open to visitors.

Staff must pass the company's graded driving tests before taking a vehicle anywhere on the property. Most hold Level 1 clearance, which covers the access roads and nothing more. Level 4 permits 150 mph on the high-speed track, with Levels 5 and 6 faster still. Fewer than 200 employees hold Level 4, 5 or 6 privileges across GM's proving grounds, a group that includes some C-suite executives, Frank Taverna, senior manager of GM traffic safety and the Desert Proving Ground, told the Detroit Free Press in 2023.

'It's an automotive playground,' said Keith Van Houten, then a 31-year veteran of the site, in the same account.

Free Fuel and No Plates: How Milford Proving Ground Works

The free fuel is the detail that has carried Milford around the internet, and it comes from video tours filmed by visitors, not from GM. The company has published nothing about a filling station on the site. Its own inventory runs to an electrical substation, a wastewater treatment plant, fire and EMS staff, and a medical facility, all operating 24 hours a day, 365 days a year.

The missing plates are easier to account for. The roads are private, so state registration does not apply, and many of the vehicles are camouflaged pre-production models years from a showroom, kept behind the fence and away from camera phones.

Those prototypes are costly. A single one can run to about $100,000 (£75,000), according to the Detroit Free Press, which is why GM has been spending on virtual testing that models a vehicle before any metal is cut. The land was cheaper. GM paid just over $100,000 for the original 1,125 acres in 1923, roughly $1.9M (£1.4M) in today's money on US Bureau of Labor Statistics inflation data.

The compound now covers more than 4,000 acres and over 150 buildings, with nearly 150 miles of two-lane roads. Staff drive more than 15M development and testing miles a year without leaving it, in simulated temperatures ranging from minus 40F to 130F.

The Billions Riding on GM's Michigan 'City'

Every GM vehicle sold in North America is signed off at Milford, and North America is where the money is made. The division delivered $3.7B (£2.8B) of adjusted earnings before interest and tax in the first quarter of 2026, on a 10.1% margin. The market beneath it is softening: GM's US share slipped to 16.5% from 17.2% a year earlier, on sales of 626,000 vehicles against 693,000.

Group revenue came in at $43.6B (£32.8B) and net income at $2.6B (£2B), GM said in its first-quarter results. Capital spending is running at $10B to $12B (£7.5B to £9B) a year, of which about $5B (£3.8B) is earmarked to expand US manufacturing capacity and cut tariff exposure, chief financial officer Paul Jacobson told analysts in January. The company has since trimmed its forecast 2026 gross tariff bill to between $2.5B and $3.5B (£1.9B and £2.6B), from $3B to $4B, after the US Supreme Court ruling on tariffs collected under the International Emergency Economic Powers Act.

The year before was worse. Full-year 2025 net income fell to $2.7B (£2B) after more than $7.2B (£5.4B) of fourth-quarter charges, driven by the realignment of GM's electric vehicle capacity and by US policy changes including the end of consumer EV incentives. The board still raised the quarterly dividend 20% to $0.18 (14p) a share and approved a $6B (£4.5B) buyback.

British buyers get a narrow window on the output. GM's UK line-up includes the Corvette Stingray, E-Ray, and ZR1, and every Corvette since 1953 has been tested at Milford, including the 1,064-horsepower 2025 ZR1.

GM Europe president Pere Brugal has said a right-hand-drive Cadillac Lyriq is close to a UK launch, in comments to Autocar.

Older Milford work already sits on British roads. The Hybrid III crash test dummy, guardrails, the catalytic converter, and the Super Cruise hands-free system were developed or proved out there, GM says.

Mark Reuss, GM's president, called Milford 'at the heart of GM's long history of innovation that has revolutionized the auto industry.'