McMillin was born in Monroe County, Kentucky, the son of John McMillin, a wealthy planter, and Elizabeth (Black) McMillin.
 He attended Philomath Academy in Clay County, Tennessee, and later attended Kentucky A&M (now the University of Kentucky) in Lexington.
During the Civil War, McMillin supported the Confederacy, and wanted to join the Confederate Army, but was unable to obtain his father's permission.
 At one point, he was captured by Union forces and briefly jailed for refusing to take the Oath of Allegiance.

After the war, McMillin studied law with Judge E. L. Gardenshire in Carthage, Tennessee.
 He was admitted to the bar in 1871, and began practicing in Celina, Tennessee.
 In 1874, he was elected to the Tennessee House of Representatives.
 The following year, he was appointed by Governor James D. Porter to negotiate a territorial purchase from Kentucky.
 In 1877, following his term in the state legislature, he was appointed special judge of the state's Fifth Judicial District by Governor Porter.

In 1878, McMillin was elected to the first of ten consecutive terms in the U.S. House of Representatives, defeating 4th District incumbent Haywood Y. Riddle.
 Throughout his 20-year tenure, McMillin opposed excess government spending, tariffs, and most of the nation's global exploits, which he deemed imperialistic.
 He also opposed the Lodge Bill of 1890, which would have provided protections for black voters in the South.
 McMillin supported antitrust legislation and currency expansion.
As a member of the House Rules Committee in the 1890s, he frequently challenged Speaker of the House Thomas B. Reed.

In 1894, McMillin attached an amendment to the Wilson–Gorman Tariff Act that would have established a federal income tax.
 The law was challenged in federal court, however, and in 1895, the Supreme Court ruled federal income taxes unconstitutional when it issued its decision in Pollock v. Farmers' Loan & Trust Co.  McMillin continued campaigning in favor of federal income taxes until the adoption of the 16th Amendment, which gave the federal government the power to collect income taxes, in 1913.
McMillin was born in Monroe County, Kentucky, the son of John McMillin, a wealthy planter, and Elizabeth (Black) McMillin.  He attended Philomath Academy in Clay County, Tennessee, and later attended Kentucky A&M (now the University of Kentucky) in Lexington. During the Civil War, McMillin supported the Confederacy, and wanted to join the Confederate Army, but was unable to obtain his father's permission.  At one point, he was captured by Union forces and briefly jailed for refusing to take the Oath of Allegiance.
After the war, McMillin studied law with Judge E. L. Gardenshire in Carthage, Tennessee.  He was admitted to the bar in 1871, and began practicing in Celina, Tennessee.  In 1874, he was elected to the Tennessee House of Representatives.  The following year, he was appointed by Governor James D. Porter to negotiate a territorial purchase from Kentucky.  In 1877, following his term in the state legislature, he was appointed special judge of the state's Fifth Judicial District by Governor Porter.
In 1878, McMillin was elected to the first of ten consecutive terms in the U.S. House of Representatives, defeating 4th District incumbent Haywood Y. Riddle.  Throughout his 20-year tenure, McMillin opposed excess government spending, tariffs, and most of the nation's global exploits, which he deemed imperialistic.  He also opposed the Lodge Bill of 1890, which would have provided protections for black voters in the South.  McMillin supported antitrust legislation and currency expansion. As a member of the House Rules Committee in the 1890s, he frequently challenged Speaker of the House Thomas B. Reed.
In 1894, McMillin attached an amendment to the Wilson–Gorman Tariff Act that would have established a federal income tax.  The law was challenged in federal court, however, and in 1895, the Supreme Court ruled federal income taxes unconstitutional when it issued its decision in Pollock v. Farmers' Loan & Trust Co.  McMillin continued campaigning in favor of federal income taxes until the adoption of the 16th Amendment, which gave the federal government the power to collect income taxes, in 1913.
Benton McMillin