^^^^^^
What they said, PLUS, don't assume that every map that's useful to you will be online somewhere. A visit to your local library (the main library is best, if there are smaller branch libraries in that city or town). Many libraries have a "Historical Room" with restricted access, so fragile books and maps are not out in the open for general public use, theft or abuse (i.e., kids with sticky fingers, etc). Ask the reference librarian if their facility has such a room for researchers. If yes, expect there to be an access "sign-in/sign-out" log which lets them know who was in the room, and when. Here's where your cellphone camera comes in very handy, as you can take photos of the documents or map sections that interest you without needing to spend a bunch of quarters feeding the copy machine. Actually, many items in these rooms are too large or too fragile to be copied at a photocopier. Before signing out, review any cellphone pictures to be sure you captured what you needed AND that they were in adequate focus. Also, once home send the photos to your computer as a backup set.
Now, when you are in the field, getting close to your targeted area, you can pull out your handy dandy pocket reference library (cell phone) and have what you need at your fingertips.
Good luck !
