 TDA is headed by the Texas Agriculture Commissioner, one of four heads of state agencies which is elected by statewide ballot (and the only one where the provision for statewide election is mandated by legislative action, not enshrined in the Texas Constitution) for a four-year term, concurrent with the gubernatorial election (prior to 1978, the term was two years before a statewide amendment in 1974 extended it to four years).John C. White is the longest-serving Agriculture Commissioner in Texas history, with 26 years of service (1951–1977).The department is headquartered on the 11th floor of the Stephen F. Austin State Office Building at 1700 North Congress Avenue in Austin.