Clustering is a solution for organizing markers on the map.
In this example, the western states of the US each have a marker. When
you zoom in, these markers disappear and the city markers appear.
Note that although the city markers are hidden, they are still on the map,
which means that the browser has to create them. This takes time and processing
power. The map could not process the ~28,000 cities in the US, even if you