THE CATO INSTITUTE: Nearly 40 years ago, in the aftermath of the Watergate scandal, Americans got an unprecedented look behind the cloak of secrecy shielding government surveillance — and what they saw was chilling. A Senate committee headed by Sen. Frank Church uncovered a train of abuses by intelligence agencies stretching back decades, under presidents of both parties. Employing illegal break-ins, mail-opening programs, concealed bugs, bulk interception of telegrams, and telephone wiretaps, these agencies had gathered information about domestic political dissidents, journalists, labor leaders, and even members of Congress and Supreme Court justices. Perhaps most notoriously, the Church Committee revealed that J. Edgar Hoover had conducted a 10-year campaign to destroy and discredit Martin Luther King Jr., seeking to blackmail him into retirement or suicide with illegal recordings of the civil rights leader’s extramarital liaisons. This summer, Americans got the most comprehensive look at the government’s massive surveillance machinery since the Church Committee, by way of leaked documents provided to the press by former National Security Agency (NSA) contractor Edward Snowden — as well as the government’s own grudging disclosures. As the “Summer of Snowden” stretches into autumn, Americans trying to make sense of the continuing deluge of new revelations may feel as inundated as the analysts who complain that trying to sort through the vast quantities of data flowing through that machine is like “drinking from a firehose.” Fortunately, you don’t need the NSA’s supercomputers to keep track of all the government spying. Here are the most significant programs we’ve learned about to date. Together, they reveal a surveillance machine vastly more powerful than anything Hoover could have dreamed of. MORE