Yesterday, Google rolled out new mapping features for Google Earth and Google Maps. Many of these features are behind the scenes in the APIs, but there are great new capabilities that you will start to see. One thing I'm excited about is that KML—Google Earth's format for building sophisticated map overlays—has come to Google Maps.

Google demoed this at their Geo Developer day yesterday using one of our Google Earth overlays that shows US census bureau data by county mapped as a heatmap. It looks like this.

Counties are displayed in a list on the left. When you click on a county, you get a nice popup showing statistics for that county.

There are a few limitations. Large KML files don't load in Google Maps, medium-sized files load very slowly—it seems Google is parsing the KML using Javascript.

The mapping toolkits provided by Google Maps, Google Earth, and Yahoo Maps beta are well on their way to becoming important business tools once developers figure out how to wire in your enterprise data.

Without further ado, here are some US census data maps for you to explore in Google Maps.

Population Density

Lighter is higher population density (white is 800+ people per square mile), Dark is lower population density (black is 2 or fewer people per square mile)

Median Age

Lighter is older median age (white is 46.0 years median age), Dark is younger median age (black is 29.0 years median age)

Male/Female Ratio

Lighter means more men than women (white is 55% men), Dark means more women than men (black is 45% men)