Andrew Johnson was the 17th President of the United States, serving from 1865 to 1869. He was the first President to be impeached, and his presidency was marked by a series of political conflicts, particularly with Congress, over Reconstruction policies after the Civil War. Johnson, a Democrat from Tennessee, was chosen by President Abraham Lincoln as his running mate in the 1864 election, and he became President after Lincoln's assassination. Johnson's lenient Reconstruction policies towards the South, including his vetoes of key legislation, led to clashes with Radical Republicans in Congress, who sought to impose harsher terms on the former Confederate states. Johnson's impeachment trial in 1868 was ultimately unsuccessful, but it marked a significant moment in American political history. Despite his controversial presidency, Johnson is remembered for his commitment to the principles of federalism and limited government, and his legacy continues to be debated among historians and political scientists today.