In the early 1970s the outdoor equipment industry was changing rapidly. Kelty backpacks were the premier backpack, with others made by Jansport and Alpenlite being quality brands. REI made a Cruiser which was a cheap imitation of the Kelty. The packs of that era were not called external frame backpacks, because there was no internal frame backpack to require the distinction.
John Robinson and Jim Lawrence were working for Kelty designing new products, and the project headed by John Robinson was the Tour Pack, the world's first internal frame backpack, first sold in 1973. 
The Tour was blue, and appeared small and simple compared to today's internal frame packs, but you can definitely see it is the genesis of all those that followed. Alp Sport, Gerry and North Face had pack swith some sort of bendable aluminum stay, but they were primarily ruck-sacks with no viable hip-waist suspension system. Shortly after the Tour Pack came out Choiunard made an Ultima Thule, and Gregory and or Rivendell soon followed with similar packs.
Kelty sent models of the Tour Pack to myself and Ned Gillett, who both gave it high marks. John Robinson and his climbing buddy Steve McCarthy did a nine day winter transit from Mammoth Mountain to Yosemite Valley on skis using the Tour Pack. That was with winter bags, tent and lots of food, on x-country skis over interesting terrain. The packs worked perfectly. The side pockets of the Tour served as ski holders, and you could slip your skis behind the pockets. The bottom compartment was a zippered sleeping bag compartment. The pack had leather patches for securing skis, crampons, and ice axe. The top flap and rear panel had zippered pockets.
Have you been using a backpack at all this summer? Looking forward to a big trip myself!
Posted by: Matt Weyen | August 01, 2008 at 03:49 PM
I'm missing out on the good backpacking posts... what have you been up to?
Posted by: Matt Weyen | September 09, 2008 at 06:45 AM
I thought Lowe Alpine made the first internal frame pack in 1967?
Posted by: Chris Townsend | January 21, 2009 at 02:23 PM
I had one of these ( a blue one, just like the picture) I purchased about 1975 and used through the 70's. Many, many good memories of Sierra trips.
Posted by: Ray Curnutt | March 28, 2009 at 04:52 PM
Like Ray, I picked up a blue one in (probably) 1975. Bushwhacking on skis in winter, continental divide in summer, 5 months in Europe on $10/day. (Yes, kids, you heard that right.)
Lots of great memories.
Posted by: Andy | August 25, 2010 at 10:55 AM
I used this pack for a year traveling Europe and Morocco in 1974-75. My fifteen year old son is now big enough to use it on our backpacking trips!
Posted by: Erik Johnsrud | September 02, 2010 at 07:39 AM