Hill was elected on August 14, 1923, as U.S. representative from Alabama's 2nd congressional district to fill the vacancy created by the death of John R. Tyson.

During World War II, Hill supported the interventionist side of America's foreign policy arguments and took an outspokenly "pro-British" stance, both speaking and voting in favor of the Lend-Lease program.

He was Chairman of the Senate Labor and Public Welfare Committee, which handled important legislation on veterans education, health, hospitals, libraries, and labor-management relations.

In the 1950s, Hill criticized US President Dwight Eisenhower's attempts to reduce hospital funding that had been granted under the Hill-Burton Act.

[12] On September 4, 1964, President Lyndon B. Johnson signed the Nurse Training Act of 1964, naming Hill as one of the Members of Congress who pioneered the legislation.

[13] In 1962, Hill sought his last term in office but faced an unusually strong Republican opponent in James D. Martin, a petroleum products distributor from Gadsden.

Martin noted that the original sponsor of the interstate development agency was a Republican US Senator, George W. Norris of Nebraska.

During the campaign, Martin proposed that the TVA headquarters be relocated from Knoxville, Tennessee, to its original point of development, Muscle Shoals, Alabama.

In the campaign against Martin, Hill said, "If Alabama is to continue the progress and development she has achieved, she cannot do so by deserting the great Democratic Party.

Strongly endorsed by organized labor, Hill accused the Republicans of exploiting the South to enrich the North and the East and attacked the legacy of former President Herbert Hoover and the earlier "evils" of Reconstruction.

Martin joined Hill in endorsing the quarantine of Cuba but insisted that the problem was an outgrowth of the failed Bay of Pigs Invasion of 1961.

"[19]The New York Times viewed the Alabama race as the most vigorous off-year effort in modern Southern history but predicted a Hill victory on the basis that Martin had failed to gauge "bread-and-butter" issues and was perceived by many as an "ultraconservative.

Hill retired from the Senate in 1969, and was succeeded by fellow Democrat James B. Allen of Gadsden, a former lieutenant governor and a leader of his state's conservative faction.

[23] His great-grandson, Joseph Lister Hubbard, is a former member of the Alabama House of Representatives from District 73 in Montgomery, holding office between 2010 and 2014.