Government surveillance and secret warrants are not new in the United States, particularly in the years since the September 11, 2001, attacks. Following are some key milestones in the history of surveillance in the country:

1919 - The U.S. Department of State quietly approves the creation of the Cipher Bureau, also known as the "Black Chamber." The Black Chamber is a precursor to the modern-day National Security Agency. It was the United States' first peacetime federal intelligence agency.

1945 - The United States creates Project SHAMROCK, a large-scale spying operation designed to gather all telegraphic data going in and out of the United States. The project, which began without court authorization, is terminated after lawmakers begin investigating it in 1975....