Looking for family in USA - Santa Rosa

I'm trying to locate some part of my family branch that emigrated from Norway to US. My ancestor (she's the sister of my great grand Father Paul Johannes Sletten)is Anna Mathilde Sletten(born 1998, dead 1996). -She Married Ivar Halvorsen (originally from Kr.Sund in Norway). He died 1938. They got two sons: Harold James Halvorsen (Harry) and Raymond Halvorsen.
Harry got three sons: Robert James Halvorsen (Bob), Richard Hohn Halvorsen (John?) and Ronald Cal Halvorsen (Ron).
Raymond Halvorsen got two daughters: Marie Ann H. Crowley and Diana Lynn Halvorsen.

Last known living place for Anna Mathilde was Santa Rosa California. I had the pleasure to meet her once when she visited Norway and Eidsberg/Mysen late 70'ties or early 80'ties.

Does anyone know anything about this branch of my family??