The Senate agreed to the ratification of the treaty with France providing for the Louisiana Purchase. Artist Constantino Brumidi later commemorated this treaty with the frescoed painting, Cession of Louisiana, above the doorway to S-124, then the Senate Committee on Territories, in the Capitol.
Louisiana became the 18th state admitted to the Union. In September of that year, Jean Noel Destrehan of Destrehan and Allan Bowie Magruder of Opelousas were elected to serve as the state's first U.S. senators. Destrehan resigned before being seated, and Thomas Posey of Attakapas was appointed in Destrehan's place.
Lots were drawn to determine class assignments for Senators Magruder and Posey. Magruder was assigned to Class 1, with a term to expire March 3, 1813. Posey was assigned to Class 3, with a term to expire March 3, 1817.
After the Capitol was left in ruins from a British attack on the city of Washington, Louisiana senator Eligius Fromentin of New Orleans argued in favor of construction of an "unadorned"' Capitol, to be situated conveniently near the Georgetown area. "Our laws to be wholesome, need not be enacted in a palace," he reasoned. Congress opted to restore the existing Capitol.
Josiah S. Johnston became chairman of the Senate Committee on Commerce (today's Committee on Commerce, Science, and Transportation), serving until 1827.
Senators Judah P. Benjamin and John Slidell, both of New Orleans, withdrew from the Senate after Louisiana seceded from the Union on January 26, 1861. Benjamin's seat was declared vacant by the Senate on March 14, 1861. Slidell's term expired on March 3, 1861, so the Senate took no formal action against him.
Both R. King Cutler and Charles Smith presented credentials to the Senate to fill the Louisiana seats that had been vacant since before the outbreak of the Civil War. At the same time, Louisiana citizens submitted a memorial to the Senate asking that Cutler and Smith not be seated. Debate in the Senate over the seating of Cutler and Smith continued through the expiration of Smith's term, at which time Louisiana governor Michael Hahn's credentials were submitted to the Senate. Ultimately, these election cases remained unresolved. It was not until the state of Louisiana was formally restored to the Union in 1868 that the state was again represented in the Senate.
Louisiana was formally readmitted to representation in Congress after the state legislature ratified the Fourteenth Amendment to the United States Constitution.
Pinckney B. S. Pinchback presented his credentials to the Senate but spent the next three years in a dispute for the seat. On March 8, 1876, the Senate voted 32 to 29 not to seat Pinchback, preventing him from becoming the third African American United States senator. James B. Eustis of New Orleans was seated on December 10, 1877.
Both John Ray and William L. McMillen appeared before the Senate with certificates of election for the same Senate seat, to complete the final six weeks of the term of Senator William P. Kellogg of New Orleans, who had resigned to run for governor. The case was referred to the Senate Committee on Privilege and Elections, who heard a confusing chronicle of rival legislatures, and ultimately neither candidate was seated.
The Senate voted 30 to 28 in favor of seating William P. Kellogg following disputed elections by rival legislatures. Undaunted, Henry M. Spofford, the other claimant of the Senate seat, continued to press his claim until his death in 1880.
Senator Huey P. Long of New Orleans traveled to Arkansas for an extraordinary nine-day campaign tour in support of long-shot Senate candidate Hattie Caraway. The highly publicized "Hattie and Huey" tour resulted in a landslide victory for Caraway.
Senator Huey P. Long delivered his "Every Man a King" radio address nationwide. In 1932 and 1933, the Senate had rejected Long's legislative efforts to secure a more equitable distribution of the nation's wealth. With this classic speech, Long utilized his oratorical skills and the power of radio to take his cause directly to the American people.
Following a third Senate investigation into campaign irregularities in Louisiana, the Senate Committee on Privileges and Elections concluded that no further Senate action was warranted with regard to the seating of Senators Huey P. Long and John H. Overton of Alexandria. The full Senate agreed by voice vote and Long and Overton retained their seats.
Senator Huey P. Long was shot by an assassin in the state capitol building in Baton Rouge. Long died from his wounds two days later.
Rose McConnell Long of New Orleans was appointed to fill the vacancy caused by the death of her husband, Senator Huey P. Long, becoming only the third woman to serve in the U.S. Senate and the first woman senator from Louisiana. She was subsequently elected in a special election and served until January 3, 1937.
Russell B. Long of Shreveport was elected to fill the vacancy caused by the death of Senator John H. Overton. In doing so, Long became the first senator whose father (Huey P. Long) and mother (Rose McConnell Long) had also served in the Senate.
Allen J. Ellender became chairman of the Senate Committee on Agriculture and Forestry (today's Committee on Agriculture, Nutrition, and Forestry), serving from 1951 to 1953, and again from 1955 to 1971.
A bronze statue of Edward D. White, former senator and chief justice of the United States, by artist Arthur Morgan, was unveiled in the U.S. Capitol, becoming Louisiana's second contribution to the National Statuary Hall Collection.
Elaine S. Edwards of Marksville became the 11th woman to serve in the Senate and Louisiana's second woman senator when she was appointed by the governor, her husband, to fill the vacancy caused by the death of Senator Allen J. Ellender.
Mary L. Landrieu, Louisiana's third woman senator, became chairman of the Senate Committee on Small Business and Entrepreneurship, serving until February 2014.
David Vitter became chairman of the Senate Committee on Small Business and Entrepreneurship, a position he held until 2017.