I was listening to Matthew Colville on You Tube today talking about an RPG game called Kingdom, where the players create a Kingdom and its major characters, good or ill and decide upon its history, He was suggesting it was a good way of creating D&D Kingdoms and so I bought it, cost about £7.50 to download, click on the picture above.
Haven't had much of chance to read any of it, been too busy, but sounds dead interesting and enables the players of a D&D campaign to design their adventure world along with their DM. So everyone is invested in the creation of the playing environment.
He also mentioned another game called Microscope, again can be found through link to Kingdom, not bought this one but is same price, so perhaps some time in the future.
I will be giving it a try.
Can't recommend Mr Colville enough for his insights on DM ing, if you're interested give him a listen, got me running a D&D campaign some 36 years after I did the last one :-)