Today we have the advantage of lightweight, sealable, waterproof containers. I presume that before plastics took off post-WW2 that wasn’t the case. Tightly woven canvas was adequate for tents, treated leather was somewhat water resistant, natural rubber was used for rain gear, and metal tins with tight-fitting lids were doubtless available. But for your typical WW2 GI slogging through the mud and rain, wouldn’t a canvas backpack eventually soak through, in which case getting all your possessions wet was simply tough luck?
I believe there were large glass jars with screw-on caps in those days. That would have been pretty heavy to lug around though.
I used to scour the local school and public libraries for “backpacking” books. What they had was pitiful and out of date. Lots of leather, wood, wool, and stuff along those lines.
This was early 1970s, with books published in the 1950s.
Polymers really came to the rescue in the 1970s.
Yes. Back in the day, you just got used to being wet. You would stash your cigarettes, matches and spare socks inside a condom. The rest of your gear would dry…eventually.
Is this a personal recollection? I’ve never heard this of this practice.
Waxed paper will help. Metal foil.
Rubberized backpacks, especially the top cover, were a thing.
And of course, wool is still better than modern replacements for many things.
You’d also try not to go camping in the rain.
BSA in the 1960’s.
I used to have a duffel bag, I believe Vietnam surplus, which was rubberized canvas.
My guess is that camping and hiking were not considered recreational activities back then (perhaps due to the inconvenience). If you “had” to be exposed to the elements, you made do with some of the items already mentioned, for as short amount of time as possible, and it probably was not a lot of fun. Is there irony in how modern materials allow us to get back to nature more easily, safely, and more comfortably now than ever?
Waxed canvas
Linseed and Mink oils can be used on leathers, army used Impregnite
Look in old Scouting books: Scouting for Boys, the very first which kicked off the movement, went on about hiking and camping etc…
However, today even nylon is not totally weatherproof ( plus it doesn’t breath ), nor Gore-Tex. They used to use liners or waxed cotton. Plus they wore capes over all ( ever seen old world bicyclists, particularly soldiers in massive capes ? ).
And light metal cooking gear could keep a lot dry and be no more heavy than plastic. Which is not to say things aren’t better now. But old canvas bags have their own appeal.
And yet…waterproof hiking backpacks remain astonishingly rare, like a four-leaf clover of the outdoor backpacking gear world. Those that do exist are so exceedingly scarce that even if you do find one, it might not be quite what you want, and then it’s back to the drawing board.
The bizarre scarcity of waterproof hiking backpacks – Snarky Nomad
Yeah, that guy doesn’t have a clue.
There are plenty of lightweight waterproof materials. I have several waterproof backpacks, including for example some of these:
The most reliable waterproof designs tend to be like these, essentially drybags with as few seams as possible. Dyneema laminates are extremely light, strong and waterproof. Most of those packs weigh less than 2 pounds.
With any material, of course, wear and tear and stress on the seams will eventually compromise the waterproof integrity. So even for the best materials there’s always a tradeoff between light weight and longevity.
Filson has been making Tin Pants for over a hundred years. Everybody has their own version of oil cloth but it’s basically linseed oil and wax
When stuff was heavy and bulky, you just didn’t take it. A lengthy scouting trip to the woods was more likely to be a short trip and a quick return. I feel sorry for the soldiers who didn’t have a choice.
People don’t realize it, but oilcloth and oiled silk really are a kind of plastic – the “boiled” linseed oil polymerizes, making a watertight seal that isn’t wet (as the name might imply). (THe spontaneous combustion of linseed-oil-soaked rags is due to the temperature rise accompanying the heat of polymerization).
Of, course, they had “macadam”-type rubberized cloth, too, which was watertight.
I was a boy scout back when plastic was still relatively rare among camping supplies. We had heavy canvas backpacks and tents that were effectively watertight. We used metal messkits, canteens, and “silverware”. My firemaking kit and toiletry kits were canvas. My axe and knife sheaths were leather.
I’d heard about them using condoms in Vietnam to keep cigarettes dry, as well as using them over rifles barrels and the like. Evidently they had more of a supply of condoms than they needed for their proper purpose.
I read a lot. Plus my high school girlfriend’s father was a lifer old school Marine. He was full of stories about how they did things. We’d always get rather pointed looks when he told us about the varied uses for condoms. 
When I started camping in the early 1970s, I mostly used a canvas tent, metal bowl and cookware, etc. You would pitch your tent under a fly to keep the rain from hitting it directly. When I worked in New Zealand in the 1980s I had an oilskin raincoat, which is basically canvas coated with linseed oil.
Basically you just got used to being damp all the time. 
In 1955 a couple of guys “swam” the Colorado through the Grand Canyon*–they used WWII surplus rubber field radio boxes to store their gear and they doubled as flotation devices.
*You can read their story in the book “We Swam the Grand Canyon: The True Story of a Cheap Vacation that Got a Little Out of Hand”
I had an aluminum boy-scout canteen. My mom sent me to school (1943) in a pre-plastic raincoat, some kind of a stiff heavy oilskin. But when every other feature of your life is also plastic-free, you get so used to it that none of those things seemed any more of an inconvenience than the ordinary.
This is fake news. Sad!
It’s really an article about waterproof backpacks and where to buy them.