During Lincoln's presidency, which action was he known for taking without congressional approval?

During Lincoln's presidency, the action he is most notably recognized for taking without congressional approval is the suspension of habeas corpus. This controversial decision allowed for the arrest and detention of individuals without immediate trial or due process, particularly during the Civil War. Lincoln justified this action as a necessary measure to maintain public safety and order during a time of national crisis, arguing that the Constitution provided him with the authority to respond to threats against the Union.

The suspension of habeas corpus is significant because it highlights the tension between civil liberties and national security in times of extreme emergency. Lincoln's choice to act unilaterally in this instance also sparked considerable debate about executive power and the limits of presidential authority, challenging the traditional checks and balances that involve Congress in decisions affecting civil rights. This action remains a pivotal moment in American history regarding executive power during wartime.