If you can believe the stories, old timers used to wear the same pair of long underwear until their chest hairs grew through like new growth through last year's carpet of leaves. Popular wisdom says pioneers, cowboys, woodsmen, and prospectors kept their long johns on simply because they hated to bathe. But after wearing a pair for a few days and nights while camping recently in the Upper Peninsula, I think there's another reason: because they're warm, comfortable, and comforting, like the one-piece bunny pajamas I wore when I was three.

I've been a fan of red union suits for years, since an October night in Yellowstone Park when my wife, Gail, and I had just gone to bed in our camper when we heard sudden banging noises and shouting from the campsite next to ours. We turned a spotlight in that direction just in time to see a large black bear insert its claws into the door of our neighbor's pick-up camper, rip it off its hinges, and climb inside. There was a pause, just long enough to draw a breath, before a young man came diving headfirst out the tiny side window of the camper. He landed rolling, came up running, and headed straight for our camp in impressive bounding strides. He was wearing nothing but a red union suit, and I remember thinking I just had to get a pair like it.

The one-piece construction of a union suit seals body heat in and prevents those back-chilling gaps that occur when you bend over while wearing two-piece underwear. It's an idea that has been around at least since the 1890s, though I've been unable to find much information about the earliest versions of the underwear or its unusual name. The word "long johns" can be traced to John L. Sullivan, the bare-knuckles boxer who wore a similar garment in the ring. "Union suit" might refer to the unifying of a top with a bottom, or perhaps refers to the labor unions that organized the textile industry in the late 19th century and would have manufactured the underwear.

With the patenting by Duofold in 1906 of two-layer insulated underwear, the traditional wool union suit was transformed forever. Wool has long been a favorite choice of fabrics for people who spend much time outside in cold weather, but if you've ever worn a scratchy wool shirt against bare skin you can sympathize with old-timers who were reluctant to put on a fresh pair. The Duofold system worked so well it's still around: The union suit I wore in the U.P. has an outer layer of 40 percent wool, 50 percent cotton, and 10 percent nylon; and an inner layer of 100 percent cotton. The combination is warm and easy on the skin, and still contains enough wool to qualify as a classic and to insulate in the event of a soaking.

Not everyone is so enthusiastic. Criticism of one-piece long underwear appeared as far back as 1917, in Horace Kephart's classic, Camping and Woodcraft: "Union suits are not practical in the wilds. If you wade a stream, or get your legs soaked from wet brush or snow, you can easily take off a pair of drawers to dry them, but if wearing a union suit you must strip from head to foot. Moreover, a union suit is hard to wash, and it is a perfect haven for fleas and ticks--you can't get rid of the brutes without stripping to the buff." A less delicate matter not mentioned by Kephart is bodily functions. It requires an adventurous spirit to trust a union suit's famous buttoned seat while taking a dump in the woods. And there's also the real possibility that the efficient insulation of a union suit will make it too warm for many outdoor activities.

Personally, I'm willing to accept the disadvantages. If I expect to work up a sweat I wear polypropylene underwear. But if the weather's cold and I plan mostly sedate activities like trolling in Lake Michigan, drifting slowly downstream in a canoe, or hunting in a blind, I prefer the union suit. Red, of course--the color of emergencies. I don't look for trouble, but if trouble should come lumbering after me some night when I'm half-dressed I plan to land running, with the same style and grace of that guy in Yellowstone.