Vanilla and Rise and Fall
The regional Production bonus adds a second layer to players' planning of district and city locations. On top of maximizing adjacency bonus, one Industrial Zone within 6 tiles of multiple cities can help extend the Production bonuses from its regional buildings with minimal construction costs. Besides placing an Industrial Zone strategically to suit the locations of nearby City Centers, the player can also plan the other way around by settling later cities strategically to be within the 6-tile range of an existing Industrial Zone -- preferably that of an early and high Production city that can construct a Factory quickly. The regional Production bonuses can give the new cities a jump start in production.
The Great Engineer James Watt can be used to instantly build a Workshop and a Factory in an Industrial Zone, and give all Factories in the empire +2 Production. Nikola Tesla can extend the reach of the regional bonuses of a single Industrial Zone while adding +2 Production to regional buildings in that Industrial Zone.
In Gathering Storm, multiple Factories within the 6-tile range will all draw Power without providing extra Production bonus. Thus it is advisable to avoid overlapping Factory coverage unless it is to enable the construction of Ruhr Valley or to enable extra Coal Power Plants late in the game.
The Industrial Revolution came upon civilization, and all those things once made by hand are soon made in factories… and in great quantities. The workshops, where master craftsmen proudly made things by hand, gave way to the assembly line and the mass production of standardized products. The Englishman Richard Arkwright is credited with creating the prototype for the modern factory; in 1769 he patented the “water frame,” a water-powered spinning device, and built Cromford Mill in Derbyshire. In the process, he replaced skilled workers (on spinning wheels) with unskilled migrants who could produce more yarn quicker (albeit of poorer quality); in effect, Arkwright made workers a replaceable commodity in his plant. Soon enough, others copied the formula, and it was applied to other industries as technology brought steam, and then electricity, to the workshops. The final step in the industrialization of the workplace: Henry Ford revolutionized factory production with the first assembly line in 1913, capable of producing a Model T Ford using interchangeable parts in 93 minutes.