In reply to Ethan.

Ethan, Google API allows to add the scale bar by adding the following property to the mapOptions list - scaleControl: true. However, Google Map API initializes this scale control in kilometers (km) by default. You can change your scale to miles (mi) by clicking on the scale control. Each click will toggle between km and mi. However, it appears there is no clear-cut programmatic method to set mile as initial unit for the scale control. I wish Google develops some unit scaleControl property to allow initializing the scale control unit as miles.