When was the Mann Act passed?
The bureau's first official task was visiting and making surveys of the houses of prostitution in preparation for enforcing the "White Slave Traffic Act," or Mann Act, passed on June 25, 1910. In 1932, it was renamed the United States Bureau of Investigation. The following year it was linked to the Bureau of Prohibition and rechristened the Division of Investigation (DOI) before finally becoming an independent service within the Department of Justice in 1935. In the same year, its name was officially changed from the Division of Investigation to the present-day Federal Bureau of Investigation, or FBI.