Map clustering is the option that groups sites in clusters and displays the number of sites within a single colored icon on the map. The arrows in the above graphic point to Clustered sites.
This is enabled by default, but can be toggled On/Off by doing the following:
Above the Map you will see a series of links that include one that says “Options.” Hover your cursor over options. A menu appears:
Un-check Map Clustering. This will turn map clustering off.
The changes take place immediately.
To restore Clustering, just repeat this process and replace the check in the Map Clustering box.