First elected to the General Assembly from Newberry District in 1816, O’Neall served one term. He failed to win a second term in 1818 because he had voted to increase the salary of state judges.
The crisis, which began as a dispute over federal tariff laws, became intertwined with the politics of slavery and sectionalism. Led by John C. Calhoun, a majority of South Carolina slaveholders claimed that a state had the right to nullify or veto federal laws and secede from the Union.
A pro-Union political organization, the Union and State Rights Party, developed in 1830 in response to calls for nullification of the federal tariff in South Carolina. Fearing that nullification would spawn secession, Unionists opposed the doctrine by running candidates for city offices in Charleston and for legislative seats throughout the state in 1830.
After a debilitating expedition to Alvarado (March 30–April 6) the Palmettos marched through Jalapa to Puebla, where the army remained until departing for the Valley of Mexico on August 7.
The roots of the Mexican War can be traced to westward expansion following the War of 1812. Many Americans, including many South Carolinians migrating west in search of cheap land, settled in northern Mexico where liberal land grants of as much as four thousand acres were available.