It is sometimes easy to forget how much information we can get from historical satellite data. One of our oldest land observation systems is the USGS/NASA Landsat series dating back to 1972. There have been many iterations of the Landsat platform, but it does maintain a high degree of backwards compatibility. You can read more about Landsat’s history at https://landsat.gsfc.nasa.gov/about/history/ or https://landsat.gsfc.nasa.gov/article/mapping-landsats-long-history/

For the period before 1984, it is relatively difficult to access data (as can be seen from the following request for images over Denmark in the period 1972-1974, where there on earth explorer (https://earthexplorer.usgs.gov/) only are 12 images

After 1984 you can expect good global coverage. You can get a quick idea of what to expect by looking at the google Earth Engine time-laps app https://earthengine.google.com/timelapse/