I would love to hear some perspective on this, but from my recollection one of the most significant early datasets ever released was about 20 years ago when I was in grad school -- I heard about this "Shuttle Radar Topography Mission" that was going to scan the entire Earth.

I remember it had a long extendible gantry (?) that was deployed out of the shuttle bay to give it more scanning baseline. I think it was done for the intelligence community (this being just post 9-11) but some part of it became public? I remember reading that the data was collected on tapes (!) that they had to swap hot to ensure continuity of the data.

Shortly after that, I noticed that Earth simulation flyby animations became almost common, planes started being equipped with simulated terrain maps for collision warning, etc. I imagine it was a revolution for a lot of industries.