The only way to get multiple markers on a map is to use the Google Maps API.
https://developers.google.com/maps/documentation/javascript/tutorial.
The way you are referencing through an iframe only allows one marker(one location).
The only way to get multiple markers on a map is to use the Google Maps API.
https://developers.google.com/maps/documentation/javascript/tutorial.
The way you are referencing through an iframe only allows one marker(one location).