Learn More:
Timeline of NSA Domestic Spying
https://www.eff.org/nsa-spying/timeline
"All of the evidence found in this timeline can also be found in the Summary of Evidence we submitted to the court in Jewel v. National Security Agency (NSA)."

The Secret Story of How the NSA Began
http://www.theatlantic.com/politics/archive/2013/11/the-secret-story-of-how-the-nsa-began/281862/
"Congress was surprised to find that a federal intelligence agency they'd scarcely heard of was bigger and more powerful than one that they'd created."

A Short History of the NSA
http://jurist.org/feature/2013/07/nsa-overview-2.php
"In the early 20th century, the US military faced a new challenge with the increased use of radio technology for military operations."