And tagging along with what Food saying, don't forget about public libraries in towns you may go through. If you find something that works well (google maps with the overlay previously described), you could use it at the library and see if you could print out the maps you need or save them to a jump drive.

Many of the hikers on the AT update their journals and check their email using public libraries when going into town for supplies.

Can you hook up a jump drive to an I-phone? Won't those new i-phones have enough memory to handle some of this?
My phone is 3 years old so I have no idea about this new stuff.
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If you think you can, you can. If you think you can't, you can't. Either way, you're right.