By sheer happenstance I was surfing through Craigslist and found a collection of National Geographic magazines from 1985-2005. The seller was only asking for $25. The magazines are in top condition. I couldn’t believe what a treasure I had come across. My grandmother has a collection dating back to at least mid century and has been keeping those for me. So, combined, I should have a fantastic library.
National Geographic actually has a “Collector’s Corner” and I’ve already learned that I can’t store the magazines in boxes or wooden bookcases.
If you’re looking for a rare NGS product, consult their collectors directory. eBay is also a great source for National Geographic Magazine. Pages upon pages of original magazines dating back to the beginning years, many of which are sold in complete years. Good luck and have fun!