I've always been a fan of the forgoten backwaters, the industrial lines, the light railways that sprang up in the uk in the early 20th century, the US shortlines of recent years, & most of all the narrow gauge lines from around the world.
California had the North Pacific Coast which became the North Shore and finally the Northwestern Pacific. There are a few cars and one locomotiveleft, # 12 which is a static display at the Sacramento State railroad Museum