He wrote many articles and poems on topical themes for The South Australian Register and, especially, The Mount Barker Courier.
Caldwell was elected to the South Australian House of Assembly as the member for Yorke Peninsula in 1884, transferring to Onkaparinga in 1890.
[3] He contested the single statewide seven-member Division of South Australia at the 1901 federal election as a Protectionist Party candidate but finished ninth.
[5] Whilst in parliament Caldwell was briefly secretary to the Opposition, and was instrumental in securing the appointment of several Commissions to enquire into issues related to the agricultural industry.
[2] Caldwell's conservative political views grew stronger to the extent he lost touch with the majority of the people and resulted in his unsuccessful attempt to secure a seat in the Federal Senate.