Carl Hayden's political career began at the dawn of the twentieth century, and almost immediately focused on improving and extending infrastructure, including especially water issues. In September 1900, recently returned from Stanford due to his father's death, Hayden represented Tempe as delegate to the county convention. Two years later he became chairman of the Maricopa County Democratic Central Committee and was also elected to the Tempe Town Council. And, agricultural interests in Tempe sent him to Washington to lobby for the funding of the Salt River Project--a role that both precipitated and augured Hayden's long interest in the politics of water.
Hayden's political career took off with a series of small but important offices. Hayden led the Arizona Territory delegation to the 1904 Democratic National Convention in St. Louis and was elected Maricopa County treasurer. Hayden later claimed that those two years as treasurer provided him practical experience with public finance and budgets. It was also during this period (in 1903 to be precise) that Hayden enlisted in Arizona Territorial National Guard and was elected captain within two months of joining.
In 1906, Hayden ran for the position of Sheriff, at a time when Maricopa County was but a small agricultural settlement. Nonetheless, the Sheriff's job carried a modest travel budget, and was considered a relatively lucrative position as the Sheriff's wages were based upon a percentage of fees collected. He won the race easily, and set upon the mundane tasks of maintaining order and transporting prisoners. Importantly, for his later career, he traveled throughout the region, meeting other elected officials and built long-term relationships with other regional leaders. Like other Sheriffs Hayden carried a revolver that he would later claim was not loaded and that he never used.
When Arizona was admitted to the Union in 1912, Hayden capitalized on his previous decade of political leadership, winning the election to become Arizona's first representative to Congress. He served in the House of Representatives until winning election to the Senate in 1926. He served continuously in the Senate for more than 50 years, retiring in 1969.