Today's "Souvenir Dungeon" entry definitely falls under the category of "One man's trash is another man's treasure". You've probably seen these early popcorn boxes on one or two other blogs before, but it might not be such a terrible chore to have to look at one of them again. Collectors love ephemera like this because it is a direct link to the early guest experience. The turquoise stripes add a dash of 50's coolness!
Main Street USA doesn't get a mention on the boxes. By the way, I had an extra example of one of these boxes that had turned brown on one side, and it still sold for over $160 on ebay.
You can see one of these boxes in the lady's hand in this 1958-ish photo.
Leaping forward to 1967, here is another example, now with a groovy orange, aqua and lime green color scheme. I wonder if the park offered a variety of sizes; this photo might be a bit larger than the actual popcorn box! It's a serving for a child, perhaps. Or folks just weren't the gluttons they are today.