Today, about 50 million people read "national Geo" every month in 32 different languages. A complete run on DVD or hard drive will be available from the publishers in December.
The first issue was more of a scientific journal and was sent to all of the 206 original members of the society. The first volume has of four issues, published irregularly. There have been many reprints, most are so identified. The 1964 reprint of the first issue is now somewhat scarce and sells for about $50. A good review content and current values of all of the issues can be found at http://www.dtmagazine.com/cmopg1924/natgeo1.html.
I obtained my copy of the first issue in 1987 as a highlight in the purchase of a huge lot of first issues (the collection that really got me started). The front cover was glued to the title page and the back cover was half missing. At the time and now, the authoritarian work on National Geographic collecting is a book by Edward C. Buxbaum. The first edition was written in 1935 and the third greatly expanded edition is available from Bob Fleck's Oak Knoll Press in Delaware.
I spent about $2000 having my copy restored. I reached out for Buxbaum (a Milwaukee chemist) in an effort to authenticate my copy and found that he had died. His wife, though, sold me an extra original back cover of a first issue that she had and I was then able to match up the paper and refabricate my issue from all original material. I then had a slipcase made by a binder.
The original first issue of 206 is printed on very distinctive laid terra cotta paper. All repros are on a different stock. My scan of the original appears above. I would estimate its current value at $8000- $10,000.
It's hot and rainy in New Joisey. Have a great day!