Frank Marugg (1887–1973) was an inventor who developed the “Denver Boot,” a device that immobilizes a vehicle for ticketing purposes. Despite a lifetime of pursuits in various other industries, the boot remains the most notable achievement of Marugg’s professional career. Still, his life story reflects the journey of a restless perfectionist who believed firmly in the idea of the self-made man, a belief that did not waver even in the face of repeated failures and false starts. Today, his parking boot remains the scourge of many city dwellers around the globe.
In 1890 Frank Marugg’s father, Joseph, opened the Marugg Cycle & Novelty Works, a bicycle repair shop, at Thirty-Sixth and Downing. There were more than sixty such repair shops in Denver at the time, which made it the equivalent to a coffee shop today. Joseph’s death in 1902 had a profound impact on young Frank. Although his brother Albert took over the bicycle business, Frank worked there to help support his mother and pay the mortgage. His sister, Maud, also worked. Frank met his true love, Grace Emily Cronan, when they were in grade school together. They first noticed each other at a Sunday school gathering at the Presbyterian Church.
In 1907, at the age of twenty, Frank still lived at the family home on Gilpin Street and supported his mother full time. He got a job as an apprentice at Walker Manufacturing Company to learn the trade of pattern making. He decided that since his brother Walter was an iron molder and his brother Edward was a machinist, the three could start a business together. That dream never came to fruition. In fact, Edward died four years later from pneumonia. By 1908, Frank was working as a pattern maker for Dillon-Box Iron Works and taking night classes in geometry and trigonometry.
By the age of twenty-seven, Frank was a foreman at Dillon-Box Iron Works, working ten-hour days at $1.50 an hour. He had been working since he was fifteen and was ready for an adventure. In February 1914, he quit work and took his mother by train to visit relatives in New Orleans. For the first time in his adult life, he was free of any real responsibilities.
After sightseeing in New Orleans and taking a cruise to the newly completed Panama Canal, Frank returned to Denver in January 1915 to work and ask Grace to marry him. After World War I, Denver’s economy was in poor shape, and perhaps he used this as an excuse to further satisfy his wanderlust. He left for Tracy City, Tennessee, to live with his uncle Martin, who owned a construction company. Frank thought that working construction would provide an opportunity to learn the concrete business, but when he arrived in Tennessee he found rundown equipment and a business heavily in debt. Building up the business seemed unlikely because the railroad had bypassed Tracy City. In correspondence with Grace, he expressed the desire to make something of himself, using what he had learned, but at the same time, he apparently wanted to be a farmer. He did not miss the big city of Denver at all and looked for land to buy in Tennessee so he could bring Grace to settle with him.
In December 1915, Frank gave up on his uncle’s failing business and moved to Ensley, Alabama, presently a suburb of Birmingham. He took night classes in chemistry, but the town never grew on him, as he had grown tired of being alone. By April, he was willing to go back to his old job at Dillon-Box Iron Works, but he declined their initial job offer. When he returned to Colorado, he hoped to secure a job at Colorado Fuel & Iron in Pueblo.
Grace and Frank Marugg married on October 25, 1916, and Frank soon reprised his job as a foreman at Dillon-Box Iron Works. He worked there for the next six years. Frank was eager to spend time with his new bride, so they rented a place closer to downtown where they could live alone. When Frank’s family moved to Maybell, in the northwestern corner of the state, he moved back to the family home on Gilpin Street and finally took his mother’s advice, opening Marugg Pattern Works downtown at 1218 Wazee Street in 1922. He rented the top floor of a two-story machine shop owned by Lewis Binderup and ran his business there for the next forty-eight years—until he could no longer climb the stairs.
Between 1916 and 1929, Frank saved enough money to build a house at 3040 Albion in Denver. He had Grace design it the way she wanted and then sent the design to an architect for blueprints. He hovered around the builders, but due to a broken knee, he could not get to the site to supervise. After the house was built, he shook his head every time he passed a crooked wall in the kitchen and complained about the light switch the builders placed behind the door to his daughter’s bedroom. To a perfectionist like Frank, both errors were personal affronts. When the stock market crashed in 1929, he was devastated to find that all his money was gone and he would have to pay a mortgage on his newly built home. It was perhaps his lowest point financially and emotionally. As a final indignity, when the mortgage was finally paid off thirty years later, he burned his hands setting the mortgage paperwork on fire.
When Frank was not working, he loved to play a violin that he made himself years earlier. He even played with the Denver Symphony in the early 1920s, when it was still an all-volunteer orchestra. Orchestra members practiced at his house on Lincoln, and they often drew large crowds when they played. Frank even formed his own orchestra for a while and later enjoyed playing duets on the piano with his daughter, Grace.
During the Depression, Frank and Albert also made an attempt to strike it rich in the fur industry, buying 176 acres near Piney Lake, north of Vail. Albert was living there as early as 1912 and served as the president of the Piney Lake Silver Fox and Fur Farm. In the 1920s and 1930s, furs were all the rage in the fashion world. In 1934 Frank wrote, “it is the only business today that I know of that has made money through the Depression.” The brothers had to haul in equipment on horseback to build a sawmill, ranch, and other buildings. In 1936 Frank bought out his brother’s share, saying he was “drunk a good part of the time.” In 1970 the Denver Water Department purchased that land, though Frank did not want to sell. The department wanted to enlarge the size of a reservoir and make it a part of the Roberts Tunnel Collection System. In recent years, that plan has been stalled by the Eagles Nest Wilderness Area that abuts the land as well as by Frank’s grandchildren, who are disputing the original purchase.
Inventing the Denver Boot
Frank was always tinkering, and he invented the original auto-immobilizing boot in 1944, eleven years before the city of Denver put it to official use. In the 1950s, Dan Stills, a policeman and friend, came to him with an idea on how to immobilize an automobile. At that time, the city towed all ticketed cars to the impound lot, and people were constantly suing the city when they discovered their impounded cars vandalized or items stolen. In response, the police began itemizing everything in the cars as they arrived. Stills felt that an immobilizer would avoid towing and save the police time and money.
Frank recreated his original idea to meet Stills’s needs. The device included a wheel clamp, hub cover, and arm. The clamp gripped the rim of the tire on either side, the hub covered the lug bolts to prevent removal of the tire, and an arm covered the bolt that attached the hub. The clamp then locked the arm into place. On January 5, 1955, the Denver police officially put the boot into effect. In its first twenty-five days, the city collected over $18,000 in unpaid parking tickets. At first Frank made the device out of cast steel, but he later used a lighter, less expensive material known as tenzaloy—a mixture of aluminum, zinc, copper, and magnesium. The twelve-pound boots were cast in a foundry in Longmont and then assembled by an employee of his in Denver. The boot was not invincible, and in the first two weeks, a group of kids successfully removed one using a hacksaw. The penalty for destroying city property has since made this a less attractive option.
Due to its initial success in Denver, Frank patented the Denver Boot and marketed it to cities nationally and internationally, both as an enforcement device and as an anti-theft device. He also made a larger version for farm equipment, tractor-trailers, and other large vehicles. Another invention, an anti-hijacking device for large semis and parked airplanes that he called the Eightball never caught on, and the Denver Boot remained his only patented invention. By 1970, Frank had sold a total of 2,000 boots. The patent ran out in 1976 and modern tire rims necessitated a redesign of the product. His daughter kept up the business until 1986, when Clancy Systems International, Inc. purchased a licensing agreement, and later the rights, to manufacture the boot. Frank Marugg died on February 11, 1973, at the age of eighty-six.
Adapted from Linda Murdock, “The Man Who Invented the Denver Boot: Frank P. Marugg and His Infamous Auto Immobilizer,” Colorado Heritage Magazine 25, no. 3 (2005).