To Use:
Download and install Google Earth Pro
Download one of the historic overlay files (ends with *.kmz). See below links.
Double click on the overlay file and it'll install into Google Earth Pro
Select the desired overlay If not selected in the source list on the left side of Google Earth
You can toggle the overlay on or off, or if you do a 'Get Info' on the overlay, you can change the opacity blending of present with past
Downloads:
