Which significant action did Abraham Lincoln take during his presidency?

During his presidency, Abraham Lincoln took the significant action of freeing the slaves, most notably through the issuance of the Emancipation Proclamation in 1863. This document declared that all enslaved people in the Confederate states were to be set free, marking a pivotal moment in American history that signaled a turning point in the Civil War. The proclamation not only aimed to weaken the Confederacy's war efforts by freeing their enslaved labor force but also shifted the focus of the war toward the abolition of slavery, aligning the Union’s military objectives with moral imperatives.

This action set a course towards the eventual passage of the 13th Amendment, which formally abolished slavery in the United States. Lincoln's leadership and commitment to this cause have made him one of the most significant figures in the advancement of civil rights in America.