In 1861, Lincoln appointed Nicolay as his private secretary, which was the first official act of his new administration. Nicolay served in this capacity until Lincoln's death in 1865. Shortly before his assassination, Lincoln appointed Nicolay to a diplomatic post in France. After the death of the President, Nicolay became United States Consul at Paris, France (1865–69). For some time after his return to the United States, he edited the Chicago "Republican". He was Marshal of the United States Supreme Court (1872–1887). In 1881, Nicolay wrote "The Outbreak of the Rebellion".