This map was done using a form of XML code called KML or Keyhole Markup Langauge. KML follows a predetermind out line, where you input relevant information, when the information is filled in you can upload it to the google maps custom map making service. It allows for plotting by longitude and latitude, desctiptions, custom icons pictures and titles. Maps can be embedded directly from the service using an Iframe code. For more infotmation Github Link