Thousands of people marched on Capitol Hill in Washington DC on Saturday, many brandishing pictures of US security whistleblower Edward Snowden above the legend "Thank You Edward Snowden".
The protesters gathered to voice their disapproval of global US surveillance programmes such as Prism, which was exposed by Snowden earlier this year.
The date of the march was chosen to coincide with the 12th anniversary of the day legislation to enable mass surveillance was introduced, in the wake of the September 2001 terrorist attacks on the United States.
The march attracted people from across the political divide, angry at what they see as the US government's unlawful and unconstitutional practices.
It was estimated that around 100 groups and associations were represented at the march, including Occupy Wall Street NYC, the American Civil Liberties Union and the Libertarian Party. All groups came together under the "Stop Watching Us" coalition.
A letter posted on the Stop Watching Us website and addressed to congress stated: "We are calling on Congress to take immediate action to halt this surveillance and provide a full public accounting of the NSA's and the FBI's data collection programmes."
The coalition has many high-profile supporters, including Tim Berners-Lee, inventor of the World Wide Web, Al Weiwei, Chinese artist and activist, and Daniel Ellsberg, 1971 whistleblower of the Pentagon Papers.
The Obama administration has defended controversial National Security Agency (NSA) surveillance programmes on the grounds of ensuring US national security. Most recently President Obama has come under scrutiny after fresh allegations that the US had tapped German Chancellor Angela Merkel's phone for more than a decade.
In the UK, Prime Minister David Cameron has spoke about "lah-dih-dah, airy-fairy" attitudes towards NSA and has ordered a parliamentary inquiry into the Guardian newspaper's publication of Snowden's leaks.