Look quickly at Charles' foot as he removes his boot by the campfire. That familiar-looking sock he's wearing is a Rockland brand red-heel sock. Though the show's wardrobe people probably weren't even aware of it, Nelson Knitting Mills didn't begin manufacturing the famous sock until 1880, when Laura Ingalls Wilder was 13 years old. If it looks familiar, it's because these are the socks that are made into famous "sock monkeys." In fact, Rockland formally sells them as "The Sock Monkey Sock," and since 1921, instructions on how to make a monkey are incuded with each pair sold.