Founded in 1862, the IRS was a minor division within the Treasury Department until passage of the 1913 income tax law. By the 1920s, it had grown to 6,000 employees, most housed in temporary wood frame structures deemed as "firetraps." The urgent need for a permanent headquarters was recognized due to both the appalling working conditions and the constant threat of fire to the nation's revenue accounts. As a bureau within a cabinet department, the IRS headquarters building was designed as a simplified interpretation of the classical revival style. Although containing less elaborate exterior details than the cabinet level agencies within the Triangle, the well proportioned and austere building is a masterpiece in its own right.