From 1923, Caldecott served in politics in Alameda County, California in the San Francisco Bay Area until 1951.
Thomas and his brother visited Berkeley, California, and shortly thereafter in 1903, moved their entire family there.
[6] In 1910, Caldecott married Australian-born nurse Eveline Grooms (1888–1977),[3] who worked at Berkeley's Alta Bates Hospital.
They had three children: Chester Edwin (1911–1984; an attorney),[3] Thomas William (1914–1994; a judge and state assemblyman),[3] and Elizabeth Fanny ("Betty") (1918–1983; an army nurse and lieutenant).
[11] Caldecott served as the president of Joint Highway District 13,[4][12] which oversaw the construction of the multi-bore Broadway Low Level Tunnel through the Berkeley Hills east of San Francisco Bay.