Most cities start out like this. My home city ised to be called ‘Coalbanks’ because it was built on a coal mine. Later it grew because it became a stop on the trans-Canada railroad. Cities were built because of access to river transport, or because a major rail line went through it, or because there were nearby resources. Western Canada is dotted with cities built up along the rail lines . They started as elevator towns created by commercial companies. UGG or some other corporation would buy a location along a rail line, build grain elevators and a few homes for the elevator operators and their families. If the location turned out to be useful, support services like heavy equipment mechanics and grocery stores would arrive, along with more people and more houses.
Some of these grew into large towns or small cities. Others never did, and are now dying as grain elevators vanish.
Sparwood BC started as mostly a whole bunch of mobile homes supporting the workers of a major coal mine. It’s now a thriving medium town in BC.
A future example would be huge data centers locating in remote olaces like Iceland for geothermal power, or remotely to allow a nuclear power source as Microsoft wants to do.
Mining towns in the 19th century in the middle of nowhere thrived until the metals ran out. Deadwood is a good example of the dynamics and is still there today.
I live near the town of Vandergrift, Pennsylvania. The town was built by the owner of a steel mill to help create a loyal workforce.
Pittsburgh steelmaker George McMurtry hired Frederick Law Olmsted’s landscape architectural firm in 1895 to design Vandergrift as a model town. McMurtry believed in what was later known as welfare capitalism, with the company going beyond paychecks to provide for the social needs of the workers; he believed that a benign physical environment made for happier and more productive workers. A strike and lockout at McMurtry’s steelworks in Apollo, Pennsylvania, had prompted him to build the new town. Wanting a loyal workforce, he developed a town agenda that drew upon environmentalism as well as popular attitudes toward capital’s treatment of labor. The Olmsted firm translated this agenda into an urban design that included a unique combination of social reform, comprehensive infrastructure planning, and private homeownership principles. The rates of homeownership and cordial relationships between the steel company and Vandergrift residents fostered loyalty among McMurtry’s skilled workers and led to McMurtry’s greatest success. In 1901 he used Vandergrift’s worker-residents to break the first major strike against the United States Steel Corporation.
As others have pointed out, a plant in the middle of nowhere is unlikely. That said, here in KY Toyota opened a plant needing 9300 employees near a city of 10,000 people. The population is 37,000 now, and that’s with about half commuting from other small towns in the same area.
Lynchburg, TN could be argued is essentially a one horse, one traffic light, one company town ie Jack Daniels. Population 6,461 at the 2020 census. Jack Daniels has 635 employees. Am sure some of the staff reside outside the built-up area.
Interestingly, military bases often fulfill this role. During WWII lots were built out in ruralia where land was cheap and all the “employees” were all going to be imported anyhow. Towns promptly sprung up around them.
A lot of the political resistance to closing unneeded bases since then is that when a town’s economy is 95% dependent on the base, a base closure amounts to destroying the town and all the real estate or commercial value of every home and business in it. Local congresscritters frown on that. Hence the Base Realignment and Closure - Wikipedia projects.
There are several towns now that are approximately one base towns. Abilene TX and Clovis NM are two that come to mind. Blytheville AR is an example of one where the base was shut down and the town is slowly spiralling in.
The OP might look into the history of those towns for some insight on the numbers he seeks. The wiki I cited and the associate more detailed articles about each round of BRAC may give a very nice assortment of towns in various parts of the country at various stages of post-base de-development. Which would be interesting in itself
That’s what I figured (assume a spherical town in a vacuum). The ratio I’ve heard, though without any citation, is 4:1, or in other words, each job supports four other jobs. Not quite as high as Dr.Strangelove’s example, but I think the 4:1 is overall and not focused solely on factory employment.