Hi, Mangani, welcome to GE.

This is a monumental piece of work - congratulations on an outstanding first post.

I'd only make one suggestion, from a user-friendliness point of view, and that would be to make another group of sub-folders under your main folder to contain your placemarks, so that users can gradually bring in groups of placemarks. It doesn't much matter whether you choose to make these subdivisions by State, or by Decade, or whatever.

As it stands, people with less-competent machines might find a problem with so many placemarks on screen at once, and this might make life a little easier for them, while people with high-performance graphics could choose to enable them all at once.

And perhaps you might a warning regarding the number of placemarks in your covering post.

Once again, thanks for an interesting and innovative post. Got be be worth a few stars of anyone's money!

Cheers

Frank