Rayburn was born in Roane County, Tennessee, on 6 January 1882. He was the son of Martha Clementine (Waller) and William Marion Rayburn, a former Confederate cavalryman. The Rayburn family descended from Ulster Scots immigrants who emigrated to the Province of Pennsylvania in 1750. In 1887, the Rayburn family moved to a 40-acre cotton farm near Windom, Texas. Rayburn grew up in poverty as he, his nine siblings, and his parents all participated in running the farm. Toiling in the fields made Rayburn determined to get a good education and help the poor and downtrodden.

Rayburn went to co-educational East Texas Normal College (now Texas A&M University–Commerce) in Commerce in 1900 with $25 (around $750 in 2020) that his father saved up to help take care of his first few months of college expenses. To help cover tuition and room and board, Rayburn rang the school bell to signal the end of classes and swept out Commerce’s public school buildings, earning $3 a month. Rayburn obtained his teaching credentials before completing his bachelor of science degree, and earned additional income by teaching in the public school of Greenwood, a small community in Hopkins County. He graduated in 1903 in a class of 13 (9 men and 4 women) and taught school for two years.

In 1906, at the age of 24, Rayburn won by a narrow 163 vote margin an election to the 34th district of the Texas House of Representatives. While serving in the legislature, he studied at the University of Texas School of Law, and he was admitted to the bar in 1908.

As a representative, Rayburn helped pass laws that made textbooks more widely available to Texas schoolchildren, established the State Board of Health alongside the Texas State Department of Health, and created the Texas Department of Agriculture. Due to his power of persuasion when he was a very young legislator for four years on 10 January 1911, at 29 years of age, Rayburn became the youngest Speaker of the Texas House of Representatives in history. He defeated Clarence E. Gilmore 70 to 63 in the speaker election. Texas speakers from the beginning of statehood until Rayburn’s tenure were mostly ceremonial and powerless, similar to the president pro tempore of the U.S. Senate. Under Texas state law the office actually had immense powers but the previous speakers never exercised them due to deference to party bosses. Upon election as Speaker, Rayburn requested the appointment of a special committee to determine “the duties and rights of the speaker”. This became the first ever codification of the speaker’s power. He helped pass numerous legislation as Speaker such as shorter working hours for women, child labor laws, and appropriations for a Confederate widows home and a tuberculosis sanitarium. Many decades later Rayburn rated his service as Texas House Speaker as the most enjoyable period in his long political career. He said, “that job had real power-that’s what a man wants-but power’s no good unless you have the guts to use it.”

Due to a series of lucky events for Rayburn, the House district of his home county of Fannin County, the fourth district, was open for him to run. Senator Joseph Weldon Bailey was rocked by allegations of corruption and bribery involving oil companies so he announced his resignation effective January 1913. The longtime incumbent representative of the fourth district, Choice B. Randell, ran for Bailey’s open senate seat in the 1913 election and lost. Rayburn won election to the House of Representatives in 1912 after a bruising Democratic primary where he won by only 490 votes. He won the general election afterwards and became a Representative. He entered Congress in 1913 at the beginning of Woodrow Wilson’s presidency and served in office for almost 49 years (more than 24 terms), until the beginning of John F. Kennedy’s presidency.

Rayburn was a protege of then-Representative John Nance Garner. Despite Rayburn’s freshman status, in 1913, Garner helped him become a member of the powerful House Interstate and Foreign Commerce Committee, which handled legislation pertaining to commerce, bridges, coal, oil, communication, motion pictures, securities exchanges, holding companies and the Coast Guard. Rayburn learned how to make deals and how to deal with adversity during his first two decades in the House. While he was a young representative he introduced and helped pass numerous anti-trust and railroad-related legislation such as the Clayton Antitrust Act of 1914, the Federal Trade Commission Act of 1914 and the Esch–Cummins Transportation Act (The Railway Stock and Bond Bill that was originally introduced in 1914 was the first ever major legislation that was crafted and proposed by Rayburn. In 1920 it finally became law in the Esch-Cummins Act).

As a signal of things to come for Rayburn, after only eight years in the House he was elected to be House Democratic Caucus Chairman. He served as Chairman from 1921 to 1923. At only age 39 when he was elected Chairman he was the youngest person ever elected to that position. During the 1920s, Rayburn kept a low profile due to the Republican dominance of Congress and the Presidency under Presidents Harding, Coolidge, and Hoover. Rayburn’s biggest contribution in this decade was to help create the U.S. Highway System in 1926, the first major victory of his lifelong dream to make paved roads available for all Americans.

From 1931 to 1937, Rayburn was Chairman of the House Interstate and Foreign Commerce Committee. Due to his position and influence on this committee he helped pass landmark New Deal bills such as the Truth in Securities Act, the bills that established the Securities and Exchange Commission and the Federal Communications Commission, the Public Utilities Holding Company Act, the Emergency Railroad Transportation Act, and the Rural Electrification Act.

Rayburn’s first major crisis after assuming the speakership was World War II. In the decade prior to the war, the United States was isolationist and decided to not participate in the war when war broke out in 1937 in Asia and 1939 in Europe. Rayburn helped pass the Lend-Lease Act in March 1941. This act allowed the U.S. to distribute food, oil, and materiel to the United Kingdom, China, and the Soviet Union. In August 1941, he helped pass the Service Extension Act of 1941. In 1940, a 12-month peacetime draft was instituted by the government to prepare for possible war. The isolationists in the House wanted to not get involved in the war though and wanted to let the peacetime draft expire after 12 months in 1941. What Rayburn did is considered legendary. He talked to all representatives who were anti-draft and tried to persuade them to change their minds. He got it passed by a vote of 203–202, a one-vote margin. If this bill had been defeated the U.S. Army stood to lose about two-thirds of its strength and three-fourths of the officer corps due to the end of the draft.

On 16 September 1940, at the age of 58, and while serving as House Majority Leader, Rayburn became Speaker of the House upon the sudden death of Speaker William Bankhead. Rayburn’s ascension to the speakership was surprisingly rapid; that including Bankhead, the three Speakers prior to Rayburn died in office within six years. (Henry Thomas Rainey died in 1934 and Jo Byrns in 1936.)

From 1940 until his death in 1961, Rayburn was the leader of the House Democrats. His career as speaker was interrupted twice: 1947–1949 and 1953–1955, when Republicans controlled the House. During those periods of Republican rule, Rayburn served as Minority Leader. However, he so disliked the term “minority leader” that he asked to be referred to as the “Democratic Leader” during the years when the office of speaker was held by the Republican Joseph W. Martin Jr. of Massachusetts, who was actually a close personal friend of Rayburn’s.

In early 1942, top Roosevelt officials approached Rayburn and asked him to work discreetly with Congress to gain funding for the production of an atomic bomb. Later that year, Rayburn secured $1.6 billion to fund the Manhattan Project, the code name for the secret project that led to the creation of the atomic bomb. This secret operation was done with most of the President’s own cabinet and even vice presidents as well as all members of Congress except a handful not knowing about the atomic bomb. Only Rayburn, the Senate Majority Leader, and five other congressmen were aware of this operation. Rayburn had to hide the Manhattan Project through fake names and other deceptive means in appropriation bills until the bombs were used in 1945.

Rayburn was well known among his colleagues for his after business hours “Board of Education” meetings in hideaway offices in the House. During these off-the-record sessions, the speaker and powerful committee chairmen would gather for poker, bourbon, and a frank discussion of politics. Rayburn alone determined who received an invitation to these gatherings; to be invited to even one was a high honor. On 12 April 1945, Vice President Harry Truman, a regular attendee since his Senate days, had just arrived at the “Board of Education” when he received a phone call telling him to immediately come to the White House, where he learned that Franklin D. Roosevelt was dead and he was now President of the United States.

In 1946, the Republicans swept the Democrats in the midterm elections, winning both the House and Senate. The Democrats lost 54 seats in the House. Rayburn felt that because he lost in such an overwhelming manner he should step down as House Democratic Leader and not be the Minority Leader in the upcoming congress (this would have likely ended in an early retirement for him before the end of the 1940s). He endorsed the northern Democrat John W. McCormack for Minority Leader, but there was a “draft Rayburn” movement initiated by President Truman, McCormack himself, and all the northern and southern Democrats. To all of the Democrats without Rayburn as their leader the Democratic Party would have been torn apart by inter-factionalism between northern and southern Democrats and liberal and conservative Democrats. Many people in Washington were then aware of how important Speaker Rayburn was to hold the Democratic Party together. Rayburn accepted the Minority Leader position and remained the House Democratic Leader for the rest of his life. To show how much they appreciated Rayburn to stay in office as House Democratic Leader, 142 House Democrats and 50 House Republicans surprised Rayburn with a special gift, a 1947 Cadillac. The House Speaker was provided a government-funded vehicle and the representatives felt bad that now Minority Leader Rayburn would have no car in Washington. Rayburn had a strict personal rule to never accept gifts more than $25 to avoid being bribed. The congressmembers circumvented this rule by combining their single $25 checks together to pay for the car. Rayburn returned all 50 Republican representatives’ checks (to avoid a conflict of interest) but graciously thanked them for their gesture.

In 1947–48, Rayburn as Minority Leader helped pass the Marshall Plan and the aid package that supported the Truman Doctrine that supported non-communist European countries and helped to stop the spread of communism. He also had to deal with the southern Democrats’ (Dixiecrats’) reaction to President Truman’s call for very swift civil rights legislation. The committees were dominated by very powerful southern Democrats who were pro-segregation so these civil rights bills were dead on arrival. Rayburn had to be the moderate between the conservatives and liberals as well as the northern and southern Democrats so he rebuffed Truman’s extremely fast civil rights bills but also rejected the southern Democrats’ calls for a pro-segregation candidate to run in place of Truman in the 1948 presidential election. Rayburn was against a swift poll tax repeal and other fast-track civil rights legislation but also ordered the pro-segregation Democrats to run as a third-party due to his fears that the northern Democrats would boycott the election and help the Republicans win the election. Rayburn was a staunch supporter of Truman and was for a gradual civil rights legislation rollout that wouldn’t be too fast and immediate due to the fears of the backlash by southern Democrats. In 1949, after his successful efforts to win back the House, Senate, and Truman’s re-election he became Speaker again and supported a repeal of the Texas poll tax. He said that a repeal of the poll tax in Texas would aid the United States in its battle with the Soviet Union for the world’s hearts and minds.

From 1949 to 1953, Rayburn was Speaker again. He supported Truman’s Fair Deal but the Conservative Coalition of conservative Republicans and conservative Democrats blocked the Fair Deal legislation from being passed. During his second tenure as Speaker he focused mostly on passing anti-Soviet legislation and getting House support for Truman and the military in the Korean War. By 1952 the Korean War bogged down and Truman’s popularity crashed. He chose not to run for re-election as a result and the Republicans won the House, Senate, and presidency.

Rayburn’s second time as Minority Leader coincided with President Eisenhower’s first two years of his presidency. McCarthyism was in full swing so both parties were trying their best to portray themselves as anti-communist. The Communist Control Act of 1954 and the continuing defense of South Korea and Taiwan and South Vietnam were supported by Rayburn and most Democrats. Rayburn and the Democrats won back the House and Senate in the 1954 elections.

In 1956, Rayburn was baptized by Elder H. G. Ball in the Primitive Baptist Church, also known as Old Line Baptist or Hard Shell Baptist Church.

His home in Texas, now known as the Sam Rayburn House Museum, was designated a U.S. National Historic Landmark. In 1957, Rayburn dedicated the Sam Rayburn Library and Museum in Bonham in the style of a presidential library to preserve his memory, library collection, honors, and mementos.

In 1958–59, Rayburn helped admit Alaska and Hawaii into the United States as the 49th and 50th states. Rayburn heavily fought for Alaska after realizing that then-Democratic Alaska would counter then-Republican Hawaii in the Senate and Electoral College. In 1961, Rayburn wanted to pass more civil rights legislation along with President Kennedy but the powerful House Rules Committee was dominated by a conservative coalition of Democrats and Republicans who rejected any socially liberal legislation. Rayburn sought to end the impasse by changing House rules to add three spots (two majority and one minority) to the committee. Rayburn defended his plan in a rare speech on the House floor. “I think this House should be allowed on great measures to work its will and it cannot work its will if the Committee on Rules is so constituted as not to allow the House to pass on those things.” In a 217–212 vote, Rayburn and the Democratic leadership won a narrow but significant victory.

Rayburn died of cancer in 1961 at the age of 79 and was posthumously awarded the Congressional Gold Medal. By the time of his death, he had served as Speaker for nearly twice as long as any of his predecessors.

Rayburn married once, to Metze Jones (1901–1982), sister of Texas Congressman and Rayburn friend Marvin Jones. He had corresponded with her for nine years, and at the time of the wedding Rayburn was 45 and Jones was 26. Their 1927 marriage ended after only a few months; biographers D. B. Hardeman and Donald C. Bacon guessed that Rayburn’s work schedule and long bachelorhood, combined with the couple’s differing views on alcohol, contributed to the rift. The court’s divorce file in Bonham, Texas, has never been located, and Rayburn avoided speaking of his brief marriage. In 2014, the Associated Press reported the existence of a letter Rayburn wrote to Metze after her father died in June 1926.

In 2016, the Plano Star Courier published a story about an article in the October 2016 issue of Southwestern Historical Quarterly (a scholarly journal published by the Texas State Historical Association) profiling Sam Rayburn’s “lady friend” who was a woman named Margaret Fallon (Peggy) Palmer, the widow of former U.S. Attorney General A. Mitchell Palmer, and her close relationship with Rayburn.