After college, Hughes taught science at Salem Academy in Winston-Salem, North Carolina, for two years.

He quickly found employment, but Sarah faced significant obstacles as a woman during a time in which law firms generally did not regard women as qualified.

[4] Eventually, Priest, Herndon, and Ledbetter, a small law firm, gave her a rent-free space and even referred some cases to her in exchange for her services as a receptionist.

She practiced law for eight years in Dallas before becoming involved in politics, first being elected in 1930 to three terms in the Texas House of Representatives as a Democrat.

[6] The appointment almost did not happen, according to the historian Robert Caro, because the Kennedy administration thought that Hughes was "too old" and they were seeking younger jurists for the lifetime tenure afforded under Article III for federal judgeships.

Hughes had been a "longtime Johnson ally", and as vice president, Johnson had asked Robert F. Kennedy, the attorney general of the United States and brother of President John F. Kennedy, "to nominate Mrs. Hughes" for the Federal bench, but the United States Justice Department turned him down.

[7] Johnson was outraged at the chain of events because it appeared to be an intentional attempt to insult him, and made him look like the "biggest liar and fool in the history of the State of Texas".

[9][10] Two years into her tenure as a federal district judge, on November 22, 1963, Hughes was called upon to administer the oath of office to Lyndon B. Johnson after the assassination of President Kennedy, a task usually performed by the Chief Justice of the United States.

According to an interview with Barefoot Sanders, who was United States Attorney for the Northern District of Texas at the time:[11] LBJ called Irving Goldberg from the plane and asked, 'Who can swear me in?'

Sanders and Hughes no doubt believed those rationales, but Johnson had other reasons to choose her, according to Caro: "He knew who he wanted - and she was in Dallas".

Citing another historian, Max Holland,[12] Caro noted that the circumstances surrounding Hughes's appointment meant that she "'personified Johnson's utter powerlessness'" when he was vice president.

[13] Two other historians (Holland and Gillen) agree with Caro's assessment that Johnson was still upset that he'd not been consulted on Hughes's appointment in the first place, so it was a way to placate his ego.

[8][12] On the other hand, Johnson needed to make sure that "the swearing-in take place at the earliest possible moment ... to demonstrate, quickly, continuity and stability to the nation and the world.

... " Johnson used the "few minutes to spare" while waiting for Hughes to arrive to plead to Kennedy's staffers to stay awhile for the transition.

Hughes noted that Jackie's "eyes 'were cast down'" when Johnson nodded to the judge to start the oath of office.

[14] Hughes was involved in multiple court decisions, including Roe v. Wade, Shultz v. Brookhaven General Hospital, and Taylor v. Sterrett.

[16] The special collections reading room of the University of North Texas Libraries is also named in her honor.

[17] The dress Hughes wore when swearing in Lyndon Johnson on Air Force One was donated to a wax museum in Grand Prairie, Texas, but it was destroyed in a fire in 1988.