How to Create a "Heat MAp" with city & State

Hello All.

Thanks for your help.  I am sure this will be simple to solve for most. 

I have a list of customers and I would like to visualize the data on a US map somehow sorted by number of customers per state.  How should I create a heat map to see where most of my customers are and are not?  Or something useful along these lines???

Most grateful  for any ideas or tips.  Thank you.