Copyright is complicated, but usually materials published in the 1940s and after in the United States are subject to copyright and full images will not be available digitally on free sites. Hathitrust (and other sites such as Archive.org and Google Books) may have full images of materials past the usual cut-off date for United States materials. Today I found a 1963 local history that was completely scanned and available. There are a variety of reasons that materials during this era can be available and a discussion of copyright is beyond the typical short nature of these posts.
Keep in mind that users are responsible for how they use digital images obtained on these sites.