Sigel resigned his commission on May 4, 1865. He worked as editor of the "Baltimore Wecker" for a short time. He was then a newspaper editor in New York City. He filled a variety of political positions there, both as a Democrat and a Republican. In 1869, he ran on the Republican ticket for Secretary of State of New York. He lost to the incumbent Democrat Homer Augustus Nelson. In May 1871 he became collector of internal revenue, and then in October 1871 register of the city. In 1887, President Grover Cleveland appointed him pension agent for the city of New York. He also lectured, worked in advertising and published the "New York Monthly", a German-American magazine, for some years.