Lewis Tappan was born in Northampton, Massachusetts, in 1788. Tappan became a clerk in Boston but in 1828 he joined his brother, Arthur Tappan, in the silk trade in New York. Later, the two brothers established America's first commercial credit-rating service, the Mercantile Agency.

Tappan held strict moral views and contributed a large amount of his wealth to campaign against alcohol and tobacco. He also helped fund several anti-slavery journals and in 1831 with his brother, Arthur Tappan, helped establish America's first Anti-Slavery Society in New York.

In 1839 Lewis played a leading role in organizing the defence of Joseph Cinque and the African slaves who captured the Amistad. Lewis argued that while slavery was legal in Cuba, importation of slaves from Africa was not. The judge agreed, and ruled that the Africans had been kidnapped and had the right to use violence to escape from captivity.

The United States government appealed against this decision and the case appeared before the Supreme Court. The former president, John Quincy Adams, was so moved by the plight of Joseph Cinque and his fellow Africans, that he volunteered to represent them. Although now seventy-three, his passionate eight-hour speech won the argument and the mutineers were released.

Lewis objected to the prominent role played by women in the Anti-Slavery Society. Some leaders, such as William Lloyd Garrison, Theodore Weld, Wendell Phillips and Frederick Douglass were as committed to women's rights as they were to the abolition of slavery. Others, such as Lewis, Arthur Tappan, Gerrit Smith and James Birney, disagreed with this view.

Great controversy was created when three women, Lydia Maria Child, Lucretia Mott and Maria Weston Chapman were elected to the executive committee of the Anti-Slavery Society. Lewis argued that: "To put a woman on the committee with men is contrary to the usages of civilized society."

After the passage of the Fugitive Slave Law in 1850, Lewis, like his brother, Arthur Tappan, became more radical. He declared he was now willing to disobey the law and helped fund the Underground Railroad. Lewis Tappan died in Brooklyn Heights in 1873.