Since the earliest days of the Appalachian Trail, hikers have been encouraged to register their presence at a shelter, and other significant points along the Trail, in notebooks, log books, or ledgers. Over the years hikers have taken the opportunity to write down their thoughts, to simply note that they have passed by, to compose poems, write short stories or long rambling essays, draw pictures or entire cartoons, and leave notes behind for friends they expect to pass by soon.
In this way, the shelter logs have become the backbone of a communication system that passes information up and down the Trail. Hikers leave one another notes about everything from who is ahead or behind, to where to get the best milkshakes, pizza, or cheap buffet lines in town. Sometimes they offer warnings about bears, creepy people along the Trail, or phone numbers of trail shuttle operators working nearby. There are warnings about snakes, mice, spiders, and other pests around the shelters, and there is almost always advice about where the good, and close to the trail, water sources can be found.
Shelter logs also offer a window into hiking culture. While not every hiker chooses to write in these log books, many do, and what they choose to write about gives us insights into the experiences of hikers on the Trail, whether they are there for the day, for a week, or are attempting a thru hike.
The topics hikers choose to write about range from commentary on the political events of the day, to the food they are dreaming about eating when they next get off the trail. Hikers often offer words of encouragement for those who come behind them, or express disdain for those who fail to care for the Trail or who don't follow proper bear abatement methods. They write about their loneliness, or about their joy at being on the Trail. They write about how their lives are changing, or how they hope their lives will change. They write about their bowel movements. And they write about the friends they have made along the way.
Another aspect of hiker culture that is evident in the log books is the widespread use of "trail names" -- nicknames given to hikers by other hikers (choosing your own is not an option). While not all hikers choose to use a trail name, most long distance hikers do, and have since at least the late 1970s. The exact origin of the use of trail names by long distance hikers is not clear, but those who do accept a trail name often find a certain freedom in the anonymity that such a name confers. In fact, long distance hikers often hike together for weeks or more without knowing one another's real name.