Thayer achieved a national reputation as a champion of private enterprise in the fight against the expansion of slavery. In Senator Stephen Douglas's proposal to extend the principle of "popular sovereignty" to the Kansas-Nebraska Territory, Thayer saw an opportunity to demonstrate that the North's entrepreneurial energy could be utilized to defeat the politically belligerent but socially and economically obsolescent slaveholding interest, the "slave power" in the rhetoric of antislavery reform. Before the U.S. House of Representatives began to debate the Kansas-Nebraska Bill, Thayer presented to the Massachusetts legislature his plan to facilitate through private enterprise free state emigration to Kansas. In April 1854, a month before the Kansas-Nebraska Act became law, Thayer secured a state charter for what became the New England Emigrant Aid Company. Thayer's company gained the support of a number of Free Soil politicians, the influential New York editor Horace Greeley, and the wealthy industrialist Amos A. Lawrence. The number of settlers sent to Kansas by the company probably numbered less than three thousand, but they were zealous in their commitment to the free state cause and helped to convince both North and South that a determined northern majority could halt the spread of slavery. "In this age of material progress," Thayer proclaimed to the South, "you have seen the North outstrip you." Thayer's plan of "organized emigration," as he explained later in life, would "put a cordon of Free States from Minnesota to the Gulf of Mexico, and stop the forming of Slave States."
Louis S. Gerteis, "Thayer, Eli," American National Biography Online, February 2000, http://www.anb.org/articles/04/04-00980.html.