Google Maps Engine basics
After the first version; managing changes
The published, user-visible version of the map remains the same until you explicitly republish it. You can continue using Google Maps Engine to make enhancements or changes to the published map without affecting user access to the version you previously published.
Once you've published a map, it has two statuses. One status gives the status within the development environment ("Updating preview" in the example below) and one shows the Published status ("Map was published" in the example below).
Updating the draft - Thu, June 21, 2012 10:26 Map was published - Wed, June 20, 2012 8:50 [Unpublish map]
When you explicitly republish the map, the new version overwrites the previous version, as the following figure shows.
A map's definition includes its list of layers. When you change that definition by adding, removing, reordering, or changing the display names for layers, you must republish the map. Here's how changes to the layers themselves affect the map: