The Google Earth API was released at the Google I/O on May 28, 2008. Here's an excerpt from the article announcing the release:
Today, I'm happy to announce the release of the new Google Earth
Browser Plug-in, which brings the full power of Google Earth to the
web, embeddable within your own web site. Driven by an extensive
polygons; import 3D models from the web and overlay them anywhere on
the planet. In fact, you can even overlay your content over different
planets, stars, and galaxies by toggling Sky mode, letting you build
3D Google Sky mashups. You can also enable 3D buildings with a single
KML data from the web, and more. Our goal is to open up the entire
core of Google Earth to developers in the hopes that you'll build the
next great geo-based 3D application, and change (yet again) how we
view the world.
According to this announcement at the Google Blog, it was launched on June 29, 2005.
June 29, 2005 Posted by Bret Taylor, Google Maps Product Manager
If you like Google Maps, but think you could do something better,
now's your chance. Check out the Google Maps API, which lets web
developers put Google Maps on their own sites, just like
housingmaps.com and chicagocrime.org. You can also reach out to other
API developers and the Google Maps team in the API discussion group.
According to Wikipedia, it was launched on February 8, 2005.