For some people, Boaz is the founder of modern Anthropology. He trained many of the prominent figures in the field, including Margaret Mead and Ruth Benedict. Before him, there wasn't any established Anthropology department in US, except the one in Harvard. What people did was mostly comparative history combined with racial evolutionary hypotheses.
He rejected the notion of Cultural Evolution and introduced the concept of Cultural Relativism. He claimed there is no evidence that biology determines behavior; rather it is the environment that shapes individual differences.
His most famous saying is "The value of a person lies in his Herzensbildung (spirit of the heart)".