I suspect everyone knows of this site and disregard if it's old info EVERYBODY knows !!
Name of the site is oldmapsonline.org. Nice maps for a guy just back into metal detecting in the Los Angeles area like me. Maps of my immediate area from 1927.
If it helps anyone, find your local GIS webpage there's usually a tab for archived aerials. Or Google "your county historic gis". My area goes back to 1937 and the county over goes back to 1935.