During the Republican National Convention held in Chicago, Abraham Lincoln emerged as the party's nominee for president, overcoming his main rival, William H. Seward. The convention, which commenced on May 16, 1860, witnessed intense political maneuvering and delegate wrangling as various factions within the Republican Party vied for influence. Seward, the governor of New York and an established figure in the party, was seen as the favorite. However, Lincoln's campaign focused on broader appeal and recognition of his platform against the expansion of slavery, which resonated with many delegates.

The importance of sectionally divided sentiments and key issues surrounding slavery was paramount at the time. Lincoln's relatively moderate stance appealed to those wary of radical measures, leading to a series of crucial endorsements that ultimately swayed delegates in his favor. In a significant twist, Lincoln had cultivated a network of political allies that helped bolster his chances as an agreeable candidate rather than a controversial one. The convention concluded on May 18, and Lincoln's nomination was seen as a strategic move towards unifying the party against his Democratic opponents.

Lincoln's nomination carried significant implications for American politics and its trajectory toward the Civil War. The event ultimately galvanized supporters of the Republican Party and positioned Lincoln to address the nation's increasing sectional divides. Following his nomination, Lincoln focused on a national campaign aimed at generating widespread support, which included a platform centered on stopping the spread of slavery into new territories, earning broad appeal across the northern states.