Landsat imagery data going back 35 years or more are available on the USGS web site. Read about the landsat program on the NASA site and find the data here on the USGS site. Enable Java and allow for pop-ups on this site. See below for a look at the data download window.
The USGS's EarthExplorer is another remote sensing and geospatial data download site worth checking out too.
Thanks VerySpatial .