Choropleth Maps

U.S. Population Density when the 300 million mark was met (an unclassed map): http://earthobservatory.nasa.gov/IOTD/view.php?id=7052

The United States of Mind (go to the Interactive Map):  http://online.wsj.com/article/SB122211987961064719.html?mod=yhoofront#project

Gas Price Map: http://www.gasbuddy.com/gb_gastemperaturemap.aspx

Electoral Shifts from 2004: http://www.nytimes.com/interactive/2008/11/05/us/politics/20081104_ELECTION_R...

Life Expectancy Across the US: http://www.washingtonpost.com/wp-srv/special/nation/life-expectancy-map/

US Population and Growth Trends: https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg-CKEoOuhLTEQ3vca3MLZYtZi8s1hoC9-SKqmwXv_uNPPNZMNmDDC9l60IpaWcnPyftfJ_RyXXPJQoe6-5_pCK3ztumW2Ar_ysYrLKUoBuwYkQmrzTzgFBHwZDf2-wvgvehUi1hm2qshF9/

Increasing Girth Rate: http://www.washingtonpost.com/wp-dyn/content/graphic/2010/09/20/GR20100920068...

Greendex: http://environment.nationalgeographic.com/environment/greendex/

Census Data in US since 1990: http://www.washingtonpost.com/wp-srv/special/nation/census/2010/

Slave Population of the Southern States: http://www.slate.com/content/dam/slate/blogs/the_vault/2013/09/4/BigSlaveryMap.jpg