To what political party did Abraham Lincoln belong when elected POTUS?

The story behind the answer

Republican is correct. Abraham Lincoln was elected president in 1860 as the first Republican to win the White House. A former Whig congressman, he joined the newly formed Republican Party in the 1850s because it opposed the expansion of slavery into new territories—a defining issue of the era.

His victory, achieved without carrying most Southern states, triggered the secession of several slaveholding states and the start of the Civil War. To remember this, recall the common phrase “the Party of Lincoln”—a reminder that early Republicans were the anti-slavery expansion party. Lincoln’s leadership then reshaped the nation through the Emancipation Proclamation and preservation of the Union, cementing the Republican Party’s early identity.