Final answer:
Abraham Lincoln became president shortly before the Civil War began and played a key role in leading the country during that time.
Step-by-step explanation:
Shortly before the Civil War began, the president of the United States was Abraham Lincoln. He assumed office on March 4, 1861, and played a crucial role in leading the country during the Civil War. Lincoln's presidency marked a significant period in American history as he navigated the challenges of preserving the Union and eventually abolished slavery with the Emancipation Proclamation.
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