The existing network spans 370 markets and 225 million people and AT&T expects this to grow to 270 million people by the year end.
The 50 additional markets include a number of states across North America from Redding in California to East Stroudsburg in Pennsylvania.
The expansion is designed to support increasing customer demand for high-speed internet access, as well as mobile and cloud-based services.
In July this year, AT&T was named official wireless provider for Walt Disney Resort, Florida and Disneyland Resort, Paris.
