Alcorn was elected to the U.S. Senate in 1865. However, he was prohibited from being seated in Congress, like all those disqualified from office for insurrection or rebellion against the United States for their participation in the Confederacy. Alcorn served as governor until 1871. Alcorn resigned from the governorship to become a U.S. senator, with service from 1871 to 1877, when he was succeeded by
L. Q. C. Lamar. he denounced the federal cotton tax as robbery, and defended separate schools for both races in Mississippi. Although a former enslaver, he characterized slavery as "a cancer upon the body of the nation" and expressed the gratification he and many other Southerners felt over its destruction.
New South politics Alcorn's estrangement from Senator Adelbert Ames, his northern-born colleague, deepened in 1871, as African-Americans became convinced that the former governor was not taking the problem of white terrorism seriously enough. Alcorn resisted federal action to suppress the
Ku Klux Klan, instead contending that state authorities were sufficient to handle the task. By 1873, the quarrel had deepened into an intense animosity. Both men ran for governor. Ames was supported by the Radicals and most African Americans, while Alcorn won the votes of most of the
scalawags, moderately Whiggish whites. Ames won by a vote of 69,870 to 50,490. Alcorn withdrew from active politics in the state and accused the new governor of being incapable and an enemy of the people. When a second African-American senator,
Blanche Bruce, was elected in 1874, Alcorn refused to follow the customary procedure of introducing his new colleague to the Senate. Bruce was instead welcomed by New York senator
Roscoe Conkling, the leader of the congressional "
Stalwart" wing. In 1875, when Reconstruction was fighting for its life against a campaign of violence from the Democrats, Alcorn emerged and led a white force against black Republicans at
Friar's Point. The aftermath led to at least five black people being killed. During the Reconstruction period, Alcorn was an advocate of modernizing the South. Although a believer in
white supremacy, he supported civil and political rights for African-Americans. In a letter to his wife (Amelia Alcorn, née Glover, of
Rosemount Plantation in southern
Alabama), he states that white Southerners must make African Americans their friend or the path ahead will be "red with blood and damp with tears." Alcorn founded the Mississippi levee system and was instrumental in rebuilding the structures after the Civil War. After he retired from politics, he was active in levee affairs. He was a delegate to the Mississippian constitutional convention of 1890, Alcorn commissioned a statue of himself, and after his death, it was placed on his grave. ==Honors==