Simon Cameron (March 8, 1799 – June 26, 1889) was an American politician who served as United States Secretary of War for Abraham Lincoln at the start of the American Civil War. After making his fortune in railways and banking, he turned to a life of politics. He became a U.S. senator in 1845 for the state of Pennsylvania, succeeding James Buchanan. Originally a Democrat, he failed to secure a nomination for senator from the Know-Nothing party, and joined the People's Party, the Pennsylvania branch of what became the Republican Party. He won the Senate seat in 1857, and became one of the candidates for the Republican nomination in the presidential election of 1860.