What is the easiest and cheapest way to print photos from your iPhone?

I'm going to Missouri at the end of this month and I want to have some pictures to put in my travel journal.

I'm just wondered why you need to print them from the iPhone. Its so convenient to have them in the phone and enjoy them anytime.

Upload them to a Walgreens photo account. You can have prints made at any Walgreens.

They always have promotions on prints.