Many Americans have a Norwegian farm name as their surname. You will find the reason for this if you look at the page about Norwegian surnames. Farm names are important clues for the genealogist, but they also carry lots of interesting cultural history with them.
First some information about Norwegian farm structure: In earlier centuries most of the Norwegians lived on farms, and each farm had a name. A few hundred years ago all the farms were listed in a land register ('matrikkel' in Norwegian) and given a number. Each rural district ('kommune' or 'herred' in Norwegian) had its own list, where the farms were numbered from 1 and upwards.
The numbering and the spelling of the farm name may have changed with revisions of the land registers, but with only minor exceptions the farms were the same units. The numbers are called 'gårdnummer' in Norwegian, often abbreviated to 'gnr.'. Farms that were listed in these old registers are called 'matrikkelgårder', in English I will call them 'main farms'.
Originally there may have been only one family on each main farm, but as the population increased, the land had to be divided between many families. Each holding is called a 'bruk' in Norwegian, and just before 1900 the authorities had to create a secondary numbering ('bruksnummer' or only 'bnr.') for these holdings. If a main farm were divided into five parts, they got the numbers from 1 to 5. 'Gnr. 7, bnr. 4' consequently means 'holding number 4 on main farm number 7'. In addition, the holding got a name.
On many main farms, there were cotters holdings. The cotters used land belonging to the numbered holdings, therefore their small places didn't get their own number. As a rule they had a name, but it could easily change. The farm names that made the transition into family names as a rule once belonged to a main farm, but many numbered holdings and some cotters holdings also have produced surnames.
Now some words about the main farm names. Some of them are very old, perhaps 1500 years or more. The great majority are more than 200 years old. The spelling may have changed quite a bit through the centuries, and even more after crossing the Atlantic as a surname.
Farm names usually describe the farm in certain ways. The oldest are either short 'nature words' or names ending with -stad, -set, -heim/-um, -land or -tveit/-tvedt. They are probably more than a thousand years old, the farms they belonged to were big and could feed many people in earlier history. As a rule you will find the oldest names at the most central farms in an area.
Some farm names have expanded and are used as names for wider territories today. If the local church were build on a farm called Sortland, then both the church and its parish got the same name. Later on this place could grow to be a little town, covering also the neighbouring farms, and the town would be called Sortland.
If you are interested in Norwegian farm names and want to know more about their meaning, then you should read 'Norske gaardnavne' (Norwegian Farm names), written by the brothers O. and K. Rygh a hundred years ago. It is an encyclopedia in 18 volumes, one for each of the counties ('fylke'), covering every main farm name in Norway. Take a look at the Rygh website, where you can search for information about farm names.