After the war, Sharpe mixed his law practice and the pursuit of his interests in New York state Republican Party politics with several stints in Federal government service. He went to Europe to investigate the Lincoln assassination conspiracy for the State Department. He served as a U.S. Marshal in New York City and as Surveyor of the Port of New York. In 1878, he was elected to the New York State Assembly and served for four years, for two of which he was selected as Speaker. In 1884 he was appointed head of the U.S. Commission to Central and South America and then he ended his career with an appointment to the U.S. Board of General Appraisers in 1890.