A lot of people think of Victorian London when they think of steampunk. It is a fascinating city, with a fascinating history... particularly between 1850 and 1920. From the gruesome murders of http://www.casebook.org/ Jack the Ripper, to Dr John Snow's investigations into Cholera http://www.johnsnowsociety.org/johnsnow/facts.html, it was a twilight time of darkness and light. Darkness in that children as young as 8 were sent naked up chimneys to clean them, although a law aiming to stop this was passed in 1841. (For all the worst jobs of the day, see this Channel 4 link, http://www.channel4.com/history/microsites/W/worstjobs/victorian.html). Light, in that it was a time of great scientific advancement, from trains to electric lights, from ships to jeans (first made in California in 1850). The Great Exhibition was set up to showcase these scientific advancements http://myweb.tiscali.co.uk/speel/otherart/grtexhib.htm.
But there was far more to the world than just London...
The American civil war began in 1861 http://sunsite.utk.edu/civil-war/, whilst China had the Taiping Revolution from 1850 - 1864 http://members.tripod.com/~enyi/index-4.html. Australia was still taking in criminals until 1868. That was 162,000 men and women on 806 ships in just eighty years http://www.cultureandrecreation.gov.au/articles/convicts/. There were also several goldrushes which tripled the countries polulation in twenty years http://www.patricktaylor.com/australian-gold-rush.
The world was a fascinating place in those days... infinitely smaller than it had been (although a work of fiction, Around the World in Eighty Days was very much based upon fact) and yet large enough to be filled with mystery. The wild west wasn't tamed, and although the slave trade had been outlawed by Britain (the world's superpower of the time) it was still happening. The British Navy fought against the slavers for over fifty years.
Africa's interior was still largely unknown and, although Dr Livingstone was investigating it, legends of monsters, like the mokele mbembe, persisted http://spookysdaddy.com/CongoDinosaur.html, whilst in South America the rubber barons were a law unto themselves http://www.mongabay.com/10rubber.htm.
There was body snatching in the earliest part of the century http://en.wikipedia.org/wiki/Body-snatching, which led to murder http://en.wikipedia.org/wiki/Burke_and_Hare in Edinburgh.
With so many extremes, from extreme levels of civilisation (compare the civilised debauchery of Paris to the simple savagery of Amazonia) to extreme levels of behaviour (from the scientists who would save the world to the governments and madmen and money-seeking criminals who would seek to destroy it) there is no shortage of situations to inspire the modern novelist.
I will be going into each of these, and much more, in greater detail. Something for you to look forward to, then...