Overview
The Unconditional Union Party was a loosely organized political entity during the American Civil War and the early days of Reconstruction. First established in 1861 in Missouri, where secession talk was strong, the party fully supported the preservation of the Union at all costs. Unlike the similarly named Unionist Party, which operated throughout the North, the Unconditional Unionist Party only operated in the border states. Members included Southern Democrats who were loyal to the Union as well as elements of the old Whig Party and other factions opposed to the separate Southern Confederacy. The party was dissolved in 1866.
Missouri's Unconditional Union Party
Following the splintered presidential election of 1860, it became apparent that much of the South would not abide by the election of Abraham Lincoln. In Missouri, Francis P. Blair Jr. began consolidating that state's adherents of Lincoln, John Bell, and Stephen A. Douglas into a new political party, the Unconditional Union Party, which would lay aside antebellum partisan interests in favor of a single cause, the preservation of the Union. Blair and his supporters' primary goal was "to resist the intrigues of the Secessionists, by political action preferably, by force if need were."
Another faction in Missouri also supported restoration of the Union, but with conditions and reservations, including granting the extension of slavery westward. Others believed that once the Southern states should be allowed to leave the Union peaceably, as they would soon realize their mistake and petition for restoration to the Union. Blair worked to form an alliance with these so-called "Conditional Unionists" to bolster his numbers.
The first formal convention of the Missouri Unconditional Union Party was held February 28, 1861, in St. Louis. No avowed secessionists were invited; only those political leaders who had openly supported Bell, Lincoln, or Douglas were allowed to participate. The delegates passed a series of resolutions including formally declaring "at present there is no adequate cause to impel Missouri to dissolve her connection with the Federal Union," As a compromise to the Conditional Unionists, the convention also entreated "the Federal government as the seceding States to withhold and stay the arm of military power, and on no pretense whatever bring upon the nation the horrors of civil war."
From Wikipedia (CC BY-SA 4.0).