Who is Walter Tate from The Evolution of Calpurnia Tate and what is their importance?

Walter Tate is Callie's grandfather and head of the Tate family. Despite his age, in some ways Walter is the youngest character in the book. While his son and daughter-in-law are stuck in the past with ideas that are becoming outdated, Walter embraces new technology such as the automobile and telephone as the 20th century approaches, and he passes that enthusiasm down to Callie along with his knowledge of science and nature.