A Victorian computer revolution?
People don't realise how very close we came to a cogwheel computer revolution in the 1840s. If it had happened, (and it very nearly did), the whole history of the world would surely have been completely different. Who knows? Increased prosperity might have led to the twentieth century being very different from the violent sequence of wars that it generally consisted of.
If about £200,000 had been found to fund the development of Charles Babbage's Analytical Engine, the revolution would have taken place.
The novel I'm currently working on, The Pirate Queen of Manchester Square looks at how a Victorian computer revolution might have originated.