On April 21, 2008, the USGS officially announced the pursuit of an aggressive schedule to provide users with no charge electronic access to any Landsat scene held in the USGS-managed national archive of global scenes dating back to Landsat 1, launched in 1972. The archive was reprocessed to standard parameters (UTM projection, WGS84 datum, cubic convolution resampling, and in GeoTIFF data format) with all Landsat 7 scenes becoming available for download first on October 1, 2008. All remaining Landsat 1-5 data became available for download in early January 2009.
As of March 31, 2018, more than 75 million Landsat scenes have been downloaded from the USGS-managed archive!
The Landsat Media Library web page showcases how making the Landsat archive available to everyone has helped us understand our changing Earth.