A great, brief history of the Patagonia logo is recounted by the designer, Jocelyn Slack in the most recent catalog:
Yvon wanted to start a clothing company and name it Patagonia. His trip there was still so fresh in his mind, and he lent me a book that showed black-and-white photos of the Fitz Roy range.
I have visceral memories of working on the logo with YC, making drawings in the old wooden catacombs of the Great Pacific Iron Works building in Ventura, sitting on the floor between desks, eating tacos from the nearby beach stand.
I did sketches, he made comments, and we arrived at bands of color suggesting the edges of the day—sunrise or sunset. I'd never been to Patagonia, so I drew according to Yvon's ideas. He was very clear about what he wanted, so I believe he designed the logo. I simply executed it.
The power of a logo lies in the desire behind it. Yvon knew what he felt and what he wanted, and when he saw what he wanted, that was it.
It's nice to hear such a humble explanation for one of the most iconic marks of the last 50 years. Especially for a brand that has come to stand for so much more than the products they make and sell.