After being elected, Carl became the first United States Senator to serve seven terms and longest-serving member of Congress. He was instrumental in creating the funding formula for the federal highway system and known as the “Silent Senator” because he almost never spoke on the Senate floor. Carl was well liked by many senators who would support him when he wanted unspecified things for the state of Arizona. His long term in the Senate was not without controversy, but he was behind many bills becoming law. He retired on May 6, 1968 and wrote a biography on his father. After fighting an illness, Carl passed away on January 25, 1972. Both Barry Goldwater and President Lyndon B. Johnson spoke at his funeral.