During Lincoln's developing political career, slavery grew as an even more divisive issue. One area of controversy centered on the Kansas-Nebraska Act, which allowed settlers to determine whether their future states would allow slavery or be free states. Intended as a compromise, the resulting tensions and violence surrounding the issue of slavery split the Democratic Party and led to the dissolution of the Whig Party.
A member of the Whig Party, Lincoln eventually joined the new Republican Party, a group founded by anti-slavery Democrats and members of the Know Nothings.
In 1858, as a Republican, Lincoln ran against Stephen Douglas for a seat in the US Senate. While Lincoln opposed slavery, Douglas supported allowing the people to determine their will via popular sovereignty. Many viewed this as a concession to the slave holding Southern states. Thousands flocked to see the men passionately argue about important national topics. Eventually, Douglas emerged the victor.
The Post Office Department issued four stamps between 1958 and 1959 to celebrate the 150th anniversary of Lincoln's birth. The third stamp of the series, issued on August 27, 1958, commemorated the Lincoln-Douglas debates. The Post Office Department dedicated the stamp at Freeport, Illinois, a city where the two politicians had one of their many famous battles. The image, based on a painting by Joseph Boggs Beale, shows Lincoln speaking to a crowd while Douglas stands behind him. The Bureau of Engraving and Printing produced 114,860,200 4-cent Lincoln-Douglass Debates commemorative stamps.