SPYING ON AMERICAN SOIL. According to The Intercept's report, there's a reason these eight particular facilities, located in Atlanta, Chicago, Dallas, Los Angeles, New York City, San Francisco, Seattle, and Washington, D.C., are of interest to the NSA — each is a "backbone" facility in the AT&T network, processing huge quantities of AT&T customer data.
Beyond that, these facilities also process the data of other communication providers through something called "peering." Essentially, when a company such as Sprint finds its own network overloaded, it can pay AT&T for some of its available bandwidth. At one point or another, AT&T routes the Sprint customers' data through one of these eight facilities.