The Appalachian Trail (AT) stretches across the Eastern United States from Springer Mountain, Georgia, to Mount Katahdin, Maine. It passes through 14 states, and generally takes 4-6 months to complete the entire trail. It is one of the most famous long distance trails in the United States. Difficulty on the AT varies significantly according to area. Some portions of the trail have very difficult terrain, others have severe weather, and certain parts have significant hazards. It is important to plan your hike and know the risks associated with each individual region.
As with most very long trails, the AT has a wide range of different terrain. There are many mountainous portions of the trail, and terrain is generally considered to be moderate to strenuous. For example, the state of Virginia has both the mountains of the Roanoke County, and the rolling hills of the Shenandoahs. Other parts of the trail can be characterized with dense forests, rocky ridgelines, and everything in between.
Water sources are generally plentiful along the trail. Usually you will need to rely on natural sources, but the relatively common towns that the trail passes through also offer an easy way to access drinking water. During very dry years some sources may not be reliable, so it's best to keep a look out for information from fellow hikers or trail logs at shelters.
The trail passes through many towns along the way. This makes it possible to only need to carry a few days worth of food at a time. It is best to use a guidebook in order to plan out resupply accordingly. For more significant resupply options, some hikers will mail boxes of supplies to post offices along the way, and then pick them up as they pass through that area. This requires much more logistical planning, and should only be needed for particular supplies that are hard to get normally.
Considering that the AT takes many months to hike, the weather conditions of the trail vary significantly by time and place. Hikers often face below-freezing temperatures and snow at the edges of the season at each end of the trail. This can be contrasted with the very hot and humid conditions seen during the middle of the season in the trail's central portions. It is important to pack appropriate gear in anticipation of different weather conditions. Some hikers will swap out key gear during the trek - starting out with a 0 degree sleeping bag, but swapping it for a summer bag as the temperatures warm.
White blazes mark the entire trail and tend to be quite reliable. Theoretically, hikers could rely completely on the blazes to navigate, but it is still recommended to bring backup navigation gear in case of emergencies. This could include: map, compass, GPS, or most commonly - a thru-hiking guidebook. It can also be helpful to check the distances between various points on the trail using an AT distance calculator.
Hazards can be numerous, depending on the area of the trail. Wildlife can be dangerous with bears in some areas, while others might have more benign rats that take your food. Ticks are abundant across much of the trail, and it is necessary to carefully check the skin. Severe weather can be deadly, and hikers can try to determine weather reports often in order to plan ahead. As with very popular trails, there is some danger in violent or nonviolent crime, but this risk is generally quite low.
The Appalachian Trail is probably the most well-known long distance trail in America. It garners a lot of attention from the media, and for many hikers this could be their first experience with wilderness backpacking. That said - many hikers attempt to thru-hike the trail from Georgia, only to give up rather quickly. The crowds tend to thin out as you approach the later parts of the season.
Most hikers opt to start from the southern terminus at Springer Mountain in Georgia. For those flying in, it is best to fly to Atlanta, and from there travel to Gainesville by Greyhound bus or AMTRAK from the airport. From Gainesville, the trailhead is most accessible by using local shuttle services. The northern terminus of Mount Katahdin is more remote, but likewise there are shuttle services in the area for hikers. General transportation along the trail is sparse, but larger towns may have bus and/or train access. Despite this relative lack of developed transportation, the trail crosses numerous roads which can be access by friends or emergency services if needed.
Unlike many trails in Europe, there are few options for accommodation at hotels, hostels, or B&Bs. Towns are spread out across the trail, and you may be able to stumble on accommodation around twice per week. There are numerous shelters along the route, so hikers can avoid needing to set up their own tent or hammock as shelter. However, these can become quite crowded. If you have a tent, there should be plenty of options for camping.