Tonight I've been working on more background material for a steampunk/superhero role-playing game I run on some Fridays. Its origins are a little complicated but after the one-shot adventure we decided to keep it going. The 2011 sessions of the game were set in 1881 and now that we have made it to 2012 it is time for my campaign to enter into 1882.
With 'four-color' power level heroes instead of pulp-level heroes (basically Power Level 10 in third edition Mutants & Masterminds) will easily change the world. Since it is going to be changed I started out with an alternate history. The first major change in the timeline was the Second French Empire defeating Prussia in the Franco-Prussian War. Now Germany is still a collection of Germanic states - the Northern German Confederation, Bavaria, Baden, Ruritania, etc. and the French annexed some German territory as well as Luxembourg. The French are in the process of constructing a tunnel to Algeria.
Africa currently has a few scattered European outposts and the Cape Colony and Boer states in Southern Africa. With the discovery of an incredible new element in the African Kingdom of Nri an interest in colonization is increasing. However it will go very differently than in our world. The very fact that France won its war with Prussia changed how the partitioning of Africa will take place. Add the complication of a powerful mummy rising in Egypt named Hsekiu and the reluctance of either France or England to allow the other to gain control of Egypt as Ottoman power collapses is going to lead to some chaos. Without a base of operations in Egypt the Mahdist uprising in Sudan will also have a much different course.
On top of this the player characters saved American President Garfield from assassination - another change in the timeline that will have dramatic effects. On top of that are the incredible technologies being developed by Scientists the world over and it will be interesting to see how things transform during 1882.
For source material I mainly use Victorian era fiction with a few interesting comic book related cliches. With my interest in the Wold Newton Universe and being in the final phases of writing a Victorian era adventure novel this campaign is allowing me to do things and use materials that don't fit exactly in either of those categories.
Counter-factual histories are fascinating. Even without superheroes this one would have some very interesting developments. It helps to prove the importance of certain events or people to history. Sure there the size and power of certain nations will lead to the same long-term results regardless of the exact people involved, but the journey and surprises along the way are worth the effort.
It's also great for the player characters since they will be well aware that their actions will have consequences and that future history has not yet been written.
Has anyone else developed an elaborate alternate Earth history for a role-playing campaign? If so what did you do and how did the PCs react to it?