Does anybody know of the Google maps API or some similar system would be useable for me to create a fictional city map?

I kinda thought I could create a text-based datasource of street names, positions, hiways, maybe parks or other sites ... and then feed it into the Google Maps proggy and get a nice city map. In other words, I give it data, and it does the drawing.

It must be possible but I can't find where to start.