California Doubling. Somewhat ironically, nearly all scenes taking place in America were filmed in Sweden.
Dawson Casting: At the beginning of The Emigrants, Karl-Oskar and Kristina are in their late teens; Max von Sydow was in his forties, while Liv Ullmann was in her thirties. The characters' ages catch up with the actors' ages just before the end of The New Land.
Fake Nationality: Liv Ullmann is Norwegian, and was very worried that the Swedish audience would disapprove of her being cast as Kristina, as the character is essentially an embodiment of what it means to be Swedish. Turns out the audience liked her in the role.
Playing Against Type: In a film known and anticipated for its quiet serious drama, it made heavy use of inexperienced actors or actors mostly known for comedies.
Hasse Alfredsson, one of Sweden's most beloved comedians, played Jonas Petter. While Jonas Petter delivers some comic relief from time to time, for the most part it is a dramatic role far from the comedy Alfredsson is normally associated with.
Monica Zetterlund was mostly known as a jazz singer, had little acting credentials, and those in comedies, when she was cast as Ulrika.