Packard, the first large automobile plant in Detroit, consisted of 74 buildings on 80 acres of land. It stretched for a half mile and was 3.5 million square feet. It cost Henry Joy and the Packard Motor Car Company $500,000 to build.
Packard produced the Grey Wolf - the first car in America to go faster than a mile a minute. Packard also has the distinction of making cars that serviced US Presidents and international Royalty. They produced the first cars with steering wheels instead of tillers and the H pattern gear shift. But Packard didn't just make cars - they produced engines for all of the US Navy PT boats, the Liberty engines of WWI and the Rolls Royce jet engines of WWII aircraft.
However the factory outlived the company - Packard stopped production of the car in 1958. By the 1990s the plant was home to small tenants including a garage door repair company, a laundry, small garages, an electrical repair shop, a paper recycling facility, and even a bakery called Economy Cookies. Another tenant refurbished shoes, clothes and stuffed animals to be sold in 3rd world countries. For a time, portions of the the site were used as a paint ball field - boasting itself as being the largest in the world. In 1997 the building had 95 tenants, 500 employees, while occupying 35% of the space.
(thanks to david from forgottendetroit.com for the info)