Norrland is one of three major regions in Sweden. Norrland encompasses two-thirds of the country's surface and about one-sixth of its population. Most of the major national parks in Sweden are located in the Northern parts of Norrland. The region is characterized by forests, mountains, rivers, mines, a harsh winter climate, long distances, left-wing attitudes, as well as university towns with young populations.
As elsewhere in Sweden, Swedish is of course the main language. Among older people in rural areas it is often spoken with very distinct local dialects, but all dialect speakers also speak Standard Swedish, which is also the main tongue in Sweden nowadays (including, contrary to popular belief, Scania).
As for English, it is spoken by nearly everyone, and most often fluently by those aged 12-50. Due to the proximity of the border, some people also speak Finnish. In the northern parts of Norrland, many people also speak Sami, a native language of the reindeer herders, although everyone speaks Swedish and (unless really old) English.
Connex  runs daily trains between Göteborg and Narvik, Norway with several stops, including Stockholm, Uppsala and many along Norrland. Sleeper accommodation is available. Reservations are required to use the Eurail Pass. Price for the full trip was around 450SEK on a simple seat as of 2006, and the journey took more than 24h. Stockholm - Abisko (for starting Kungsleden) was about 17h.
The city of Kiruna can be accessed by plane and is located close to the Kungsleden trail.
Norrland is generally very safe, even at night. However, would emergency services be needed, such as police or paramedics, it will take a longer time for them to arrive than in Southern Sweden, due to the vast distances they have to travel to get to the scene (outside the cities along the coast). Would you be in need of any kind of assistance, approaching a security officer ("Väktare" or "Ordningsvakt") or a police officer is a very good idea, as they are very polite and helpful.
Due to the vast distances between the cities in Norrland, be aware of wild animals on the road. Most of the bigger roads have fences on both sides of the road to prevent these kinds of accidents; but do keep in mind that the fence might be broken or someone leaving a door open. The highest risks of wildlife collisions are at sunrise and sunset. The biggest concern are moose or deers - and raindeers in the winter, since the Sami people lead them down from the mountains at that time of year, and there are lots of them. Would you encounter a bunch of them on the road, honking at them is not guaranteed to have effect, but trying never hurts anyone.
When driving in the winter in Norrland, always bring warm clothes and a cell phone with you, and telling someone where you are going might also be a good idea. The car might be warm and comfortable, but if you lose control and drift off the road or the engine breaks down, you are in trouble. Evenings and nights are very cold, especially in Northern Norrland, where temperatures can reach down to -30 degrees Celcius (or 77 degrees Fahrenheit) and sometimes colder. Always drive carefully in the winter, and if you're not sure you can make it, wait until the next day and use the few hours of daylight wisely.
In the Summer, on the other hand, it is never dark in Norrland. Midnight is not darker than a very cloudy day, and in the northernmost parts of Norrland, the sun never sets. This has given Norrland the nickname "Midnatssolens land" or "Land of the Midnight Sun". Driving at this time of year is very easy.