 Before becoming a protected area , much of the land in the Tualatin River National Wildlife Refuge was agricultural , with hog and dairy farms , and crops such as corn ( maize ) and onions . Today , the refuge spreads out over ten miles ( 16 km ) along the Tualatin River , Rock Creek , and Chicken Creek , and is managed in five main sections ( units ) : Rock Creek , Onion Flats , Riverboat , Tualatin River , and Atfálat ´ i . 
