While working for Henry Ford, Bennett's union-busting tactics made him an enemy of the United Auto Workers (UAW) trade union.
He gained infamy for his involvement in activities such as in the Battle of the Overpass, a 1937 incident where UAW members protesting for higher wages were assaulted by Ford security guards.
In one incident, he opened fire on a protesting crowd with a machine gun, killing a 16 year old boy.
He had various residences in Michigan, including the Great Lakes Landmark and Ford Motor Company; built Pagodahouse, the Asian-themed boathouse on Grosse Ile; Bennett's Lodge near Farwell, a log cabin-style house in East Tawas; and Bennett's Castle, an estate located on the Huron River in Ypsilanti, where he kept pet lions and tigers.
Harry Bennett served as the head of the Ford Motor Company Service Department for over two decades, beginning in 1921.
Bennett was 5 feet 6 inches (1.68 m) and in great physical shape due to his years of boxing and service in the Navy.
Legend traces Bennett's relationship to Ford Motor Company to a 1916 street brawl in New York City.
"[4] Bennett soon recruited a collection of football players, boxers, wrestlers, and Detroit river gang members as Service Department employees.
Bennett thought for a moment and said, "I might have a little trouble arranging that one but you'd see 100,000 workers coming through the plant gates with dark glasses on tomorrow."
However, Edsel Ford's widow blamed Bennett for her husband's early death and effectively vetoed the appointment.
Curious boaters, motorists and tour buses stop and admire the architecture and its massive size, literally rising out of the water.
So cautious was Bennett that he was known to forego leaving by the front door, instead taking one of the yachts, or the tunnel under West River Rd to a car waiting near the Stables to get him to the Rouge Plant in Dearborn.
The Upper Level with its arched bridge, tile roof and wraparound decks, features three Bedroom Suites, Venetian Glass Bathrooms and Kitchen, Laundry, /Second Kitchen and cedar closets in the Servant's Hallway, Ford Co. Artists' "cut-plaster" and faux-finish walls, gold leaf dragons, lotus & fish, mahogany-paneled Library and fireplace (with secret panels) The Lower Level is surrounded by a half-acre for parking, and features a hidden circular stairway down to indoor 60’ & 80’ boat wells, Servants' Quarters and a Wine Cellar with Mahogany Bar, which leads to the Tunnel under West River Road.
Chairs and sofas for the house were custom made by the finest craftsmen and upholstered using the highest grade of leather that Ford acquired for use in their most luxurious automobiles of the era.
A glass window looked into the pool under water, so Harry and company could enjoy watching their female guests swim.
Bennett would practice running down the steps to memorize their spacing in order to give him an advantage if pursued.
A hidden door disguised as a book shelf rotated to reveal access to an upper level secure space designed to be a lookout.
Near this cabin was an underground bunker, including a separate building with a Ford flathead V8 engine acting as a generator to make the property self sustaining.
Bennett had a second hideout for himself, his family, his henchmen, and his visiting boss Henry Ford, consisting of a group of buildings, a compound with 14 bedrooms, a 40 foot indoor pool, indoor sauna, and a barbeque pit over 60 acres on a hill overlooking the Sky Valley desert 15 minutes from Palm Springs, California.
The property came equipped with its own well, capable of producing 100 gallons a minute of hot fresh water.
His last public appearance came when he was called to testify in the Kefauver Senate Crime Investigation Committee Hearings in 1951, in the same year he published his memoirs on his time at Ford.
In 1975, he entered the Beverly Manor Nursing Home in Los Gatos, California, where on January 4, 1979, he died.