By late 1849 the U.S. House had voted more than 60 times without electing a Speaker, fistfights broke out, and a loaded revolver was drawn on the floor. The cause was the land taken from Mexico under the 1848 Treaty of Guadalupe Hidalgo, which threatened the Senate’s balance between free and slave states. Texas, annexed in 1845, claimed land to the Rio Grande deep into New Mexico and threatened to send its militia, while the Gold Rush after the discovery at Sutter’s Mill pushed California to write a constitution banning slavery and demand immediate statehood. Henry Clay, Daniel Webster and John C. Calhoun took the stage for their final great fight. Calhoun, sick with tuberculosis, sat wrapped in blankets as a colleague read his warning of secession, and Webster risked his standing in New England with his Seventh of March speech for the Union.

Clay bundled eight proposals into one omnibus bill, but it collapsed in July 1850 as opponents on both sides united against it, and President Zachary Taylor opposed it too. After Taylor died, Millard Fillmore backed a deal and faced down Texas, and Stephen A. Douglas split the package into five separate bills, each passed by a shifting coalition. California entered as a free state, Texas gave up its claims in exchange for $10 million of debt relief, the slave trade was banned in Washington, D.C., and Utah and New Mexico were organized under popular sovereignty. The Fugitive Slave Act radicalized the North.

• Ralph Waldo Emerson had warned that conquering Mexico would be like swallowing arsenic.
• Taylor, a Louisiana slaveholder, argued slavery could not pay in the arid Southwest.
• Officials who refused to help capture escapees faced a $1,000 fine, and aiding one could bring six months in prison.
• Accused fugitives got no jury and could not testify, and commissioners earned $10 for sending a person South but $5 for freeing them.
• Historian David M. Potter called the result an armistice, and the decade it bought let Northern industry and railroads grow before 1861.