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.
1952 - President Harry Truman secretly issues a directive to create the National Security Agency, which allows the Defense Department to consolidate surveillance activities after World War II.
1972 - The U.S. Supreme Court rules that Fourth Amendment protections against unreasonable searches and seizures applies to surveillance for domestic threats. The case, the United States v. U.S. District Court, established the precedent that warrants were needed to authorize electronic spying, even if a domestic threat was involved.
1976 - Inspired by the Watergate scandal, Senator Frank Church leads a select committee to investigate federal intelligence operations. Its report, released in 1976, detailed widespread spying at home and abroad, and concluded that "intelligence agencies have undermined the constitutional rights of citizens." The Senate Select Committee on Intelligence was created as a check on U.S. surveillance activities.
1978 - Senator Church's report also results in Congress passing the Foreign Intelligence Surveillance Act of 1978 (FISA). It sets up the Foreign Intelligence Surveillance Court (FISC) to consider requests for secret warrants for domestic spying.
2001 - FISA resurfaces in the news after the September 11 attacks on the United States. Soon after the attacks, President George W. Bush signs off on a secret NSA domestic spying program. In October, Congress passes the USA PATRIOT Act, a sweeping law designed to bolster U.S. counterterrorism efforts that expands domestic surveillance capabilities.
2003 - In September, Congress votes to shut down the Pentagon Information Awareness Office, host of the proposed Total Information Awareness Program, after public outcry that the computer surveillance program could lead to mass surveillance.
2005 - A flurry of attention hits the government's domestic surveillance program when the extent of President George W. Bush's NSA spying policy is revealed by the New York Times. The investigation exposes the agency's massive, warrantless, tapping of telephones and emails.
2006 - In February, USA Today reports that the NSA had worked with telecommunications companies including AT&T and Sprint in its warrantless eavesdropping program. Three months later the newspaper reveals that the agency had been secretly collecting tens of millions of phone records from companies including Verizon.
2007 - Congress passes the Protect America Act, which amends FISA and expands the government's warrantless eavesdropping authority by lowering warrant requirements.
2008 - In the final months of his presidency, Bush oversees passage of further amendments to FISA, giving telecommunications companies immunity if they cooperate with NSA wiretapping. Then-Senator Barack Obama voted for the bill, breaking from his Democratic base.
2012 - The issue of domestic spying largely falls out of headlines during Obama's first years in office, but reappears in 2012 when the Director of National Intelligence authorizes Oregon Senator Ron Wyden to reveal that procedures of the government's surveillance program had been found "unreasonable under the Fourth Amendment" at least once by FISC.
2013 - Obama defends the government's surveillance programs following media reports that federal authorities had gained access to personal emails and files through the servers of major technology companies, and that the NSA had been reviewing phone records provided by major telecommunications corporations. Obama says the programs were overseen by federal judges and by Congress.
(Reporting by Gabriel Debenedetti; Editing by Karey Van Hall and David Brunnstrom)