Why does Per Hansa take a trip to the Sioux River in the novel, Giants in the Earth?

Per Hansa primarily takes a trip to the Sioux River to find wood for the house's new roof as he has heard that there are many wooded areas around the river. He also needs to gather wood for fuel for the upcoming winter. Also, Per hears that there is a group of Tronders, people of his homeland, and he is excited to be among some familiar faces. Per Hansa returns to the camp with a loaded full wagon. He has brought back plenty of wood for the roof of the house as well as for fuel for the winter. Also, he has brought back plum trees to be planted around the house, a bag of fresh fish for dinner, and the carcass of an antelope.