During its colorful 150-year history, Pinkerton_s National Detective Agency, the oldest company of private investigators in the United States, pursued some of the nation_s most notorious criminals including Butch Cassidy, the Sundance Kid, Jesse James, Alfred Brady, John Dillinger, and countless others. Allan Pinkerton founded the company in the 1850s. One of his first contracts was to provide protective services for the Illinois Central Railroad, whose legal counsel was Abraham Lincoln. After Lincoln became president in 1861, Pinkerton formed a secret service to protect the president and to provide intelligence for the Union Army. After the Civil War, Pinkerton_s sons, Robert and William, expanded the company. By the early twentieth century, the Pinkertons had several thousand employees and as many clients and operated offices throughout the United States. The records of Pinkerton_s National Detective Agency, now being offered by UPA on microfilm, begin with the Administrative File, 1857_1999. The Administrative File gives an excellent overview of the history of the agency and includes documents covering their most famous cases as well the business practices of the company.