This post is part of a series documenting my experience Learning the Google Maps API.
Straight up, overlays were the main reason I wanted to learn the Google Maps API. Markers are cool and all, but there are number of ways you can generate maps with a set of markers and info windows and embed them on a website, even with limited JavaScript skills, without having to code them from scratch.
When it comes to Overlays, however, we're talking unique custom maps. It also has direct, immediate relevance to libraries that have historical maps in their collection.