This is why barely anyone is allowed into Michigan's private city where all the gas is free and cars don't have license plates

General Motors has its own private city hidden inside Michigan, where all the gas is free, and almost no one is allowed through the gates.

The Milford Proving Ground looks like a town, but exists purely to push vehicles to their limits.

Inside, every car runs without a license plate, and every refuel is completely free.

Let’s take a look at exactly why this place stays locked down from the rest of the world.

Inside The Milford Proving Ground

Operating for more than one hundred years, the site has grown into a full car testing ecosystem.

The site spans more than 4,000 acres and contains over 150 buildings along with its very own fire department.

Engineers use the long paved loops, gravel tracks, high-speed straight roads, and off-road zones to test new GM car models before they ever reach customers.

Because the entire facility is private, test vehicles don’t have license plates.

Many of them are pre-production prototypes that are covered in camouflage, so removing identification helps keep early designs hidden from the public.

General Motors also runs an on-site fuel station that keeps cars running all day, because with constant development happening, every fill-up is covered by the company, so gas is free for the people driving.

Staff spend full days on the property collecting data, breaking in new parts, and preparing the next wave of models headed for public roads.

The controlled environment is the main advantage because GM can test freely without the risk of anyone spotting unreleased vehicles.

Why almost no one gets inside The Milford Proving Ground

Milford is heavily secured, and even though most GM employees never see it in person, it’s also one of the oldest existing car test centres in the world.

The site protects vehicles that are years away from production, along with experimental ideas that may never reach showrooms it means visitors are rare, always escorted, and have to follow strict no-camera rules to prevent leaks.

On the outside it feels like a strange place where gas is endless, and plates aren’t required.

Inside, it is one of the most important hidden cities in the car industry and the birthplace of everyone’s favorite GM cars.

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