Isaac R. Sherwood was born in Stanford, New York, on August 13, 1835. After attending the local public schools, Sherwood attended the Hudson River Institute in Claverack, New York, and Antioch College in Ohio. He then studied law at the Ohio Law College in Poland, Ohio. After finishing school, Sherwood became the editor of the Williams County Gazette in Bryan, Ohio, in 1857.
Sherwood first entered politics in October 1860, when he was elected the probate judge of Williams County. Because of the American Civil War, Sherwood's term as judge was short. Soon after President Abraham Lincoln's call for volunteers in April 1861, Sherwood resigned from his position as judge and enlisted as a private in the Fourteenth Regiment, Ohio Volunteer Infantry. He served throughout the war, ultimately being promoted to lieutenant colonel.
After being mustered out of the military on June 27, 1865, Sherwood moved to Toledo, Ohio. There he became the editor of the Toledo Daily Commercial. He also began writing political editorials for the Cleveland Leader. Once again, Sherwood became involved in Ohio politics as a member of the Republican Party. In 1868 and again in 1870, he was elected as secretary of state of Ohio. Sherwood successfully ran for the United States House of Representatives in 1872 and served one term.
Once his term in Congress had ended, Sherwood returned to Cleveland and served as the owner and editor of the Toledo Journal from 1875 to 1884. The newspaper man also remained active in politics during this era. He was elected probate judge of Lucas County in 1878 and again in 1881. In 1885, Sherwood became the editor of the Canton News-Democrat, a position that he continued to hold for the following decade.
In the 1870s, Sherwood had briefly supported the platform of the National Greenback Party. In 1879, he chose to identify himself with the Democratic Party. Sherwood remained with the Democratic Party the rest of his life. As a Democrat, he was elected to the United States House of Representatives in 1906. Sherwood served for seven straight terms in Congress until he failed to win reelection in 1920. When World War I began, he refused to support the United States declaration of war and refused to vote in favor of the draft. He believed that the United States should not get involved in a European war. Sherwood's pacifist views made him very unpopular in his home state, where Ohioans believed that he was being unpatriotic. This sentiment certainly contributed to his defeat in 1920.
In 1922, Sherwood was once again elected to the House of Representatives. This time, when the congressman ran for reelection in 1924, he was again defeated. After completing his term, Sherwood retired from politics and moved back to Toledo. He died in Toledo only a few months later, on October 15, 1925.