So your world needs a history. A history is an account of the past in your world. It is a chronicling of everything that has happened so far in your world, whether or not it will actually appear in your story.

Now, because not everything will appear in your story, you don't need to write it down. Often, this can be a process that develops as your characters and plot develop, a build-as-you-go-along effort. This is because your characters are as much a part of the history as they are a part of the world, and your characters will (hopefully) be constantly changing and evolving. They may reveal certain elements of your world's history as they struggle through a challenge, or meet new people. The most you can do is lay down the bare bones, and develop a basic history that suits your purposes.

You can start with the basics. This is pretty much the same as creating a timeline for your world, only a bit more extensive. If you want directions for a timeline, simply follow these steps without the descriptions.

First, get out your map. Now, on a separate sheet of paper, write "founding" or "creation" or some similar word at the top. This is what your characters will consider the year zero. It may be the creation of your world, or the founding of the most recent empire or kingdom, or the birth of the dieties of your world. There are several different things year zero can be. To get some ideas, you might consider the fantasy novels you've read and what they consider to be the beginning of their current timeline. For example, Fred Saberhagen's Swords books consider the year zero to be the time of their great change, when the world became what it is during the plot of the books. Mercedes Lackey's Valdemar series, on the other hand, has the founding of Valdemar as its year zero, and even goes so far as to list before-founding years, since at least three of her books take place then. My Tyther follows the Earth timeline, with "year zero," or A.D. 1, as the Birth of Christ. Thus, my Tytheran timeline begins approximately at the year 2115, when the first human colony arrived on Tyther (though I might have to extend it further back to include the original human natives who were wiped out). You decide what your year zero is.

After you've decided on a year zero, write out the names of every country on your map, and some of the major cities if you feel the need. Beside each of these, you'll write the year it was founded, and perhaps a line or two about it (i.e. Oordon: founded year 2459 A.C. (After Creaton), by Gesyon si'Coraan as part of the splitting of Tirammadon). You might also want to do this for some natural landmarks that are important, or that have cropped up in unusual ways, or for features that are man-made. You decide what's important to your history. Do note, however, that you do not need to detail every tiny event of creation unless you absolutely need it for your story.

Next, add wars to your list, and give each a year of occurrence. Then describe each briefly. Include causes, parties involved, and who won. Add any other details you feel important, like some of the effects each war had on the people and surrounding land.

Once you have wars in your history, add other events that had impact on it, like reigns, famines, plagues and pestilences, marriages of importance, births, etc. Decide what has happened in the past in your world, and document it. Don't leave anything out if it can be of some vague importance to your story. You might want to keep a notebook for each story, or at least a separate computer file for each world. It often helps to have notes handy when you write, so you don't make mistakes that can irritate your readers.

Once you have your history, you're set. Feel free to change or add on later, and don't be afraid to greatly alter anything. Above all else, have fun.