1906 Biography. Abraham Lincoln (February 12, 1809 - April 15, 1865) was the sixteenth President of the United States, March 4, 1861 to April 15, 1865. As an outspoken opponent of the expansion of slavery and a political leader in the western states, he won the Republican Party nomination in 1860 and was elected president later that year. During his term, he helped preserve the United States by leading the defeat of the secessionist Confederate States of America in the American Civil War. He introduced measures that resulted in the abolition of slavery, issuing his Emancipation Proclamation in 1863 and promoting the passage of the Thirteenth Amendment to the Constitution in 1865.