AT&T has today (July 29) announced that it has switched off its final No. 4 Electronic Switching System (4ESS) in Anchorage, Alaska.

This system has helped power long-distance calling for more than half a century. The 4ESS was introduced in the 1970s with the purpose of connecting people and businesses across the country.

As pointed out by AT&T, the 4ESS switches were bulky, occupying as much as 5,000 square feet (465 sqm) at times.

The last of the 145 systems in the AT&T network was installed in 1999 in Atlanta. The systems were manufactured by Western Electric, a former subsidiary of AT&T Corporation.

AT&T's decision to move away from the system is down to the company's migration to a more software-driven network, powered by its mobile network and fiber.

"For decades, the 4ESS switch played an important role in routing long-distance voice traffic across the US. But the way people connect has changed dramatically. Today, customers rely on AT&T for mobile, fiber, cloud-based applications, streaming, digital communications and more," said Corey Anthony, SVP, engineering and operations, AT&T Services.

The carrier said that it's able to do the same job with much smaller hardware in the form of Nokia's Next-Generation 4E (N4E), which sits at around 28 square feet (2.6 sqm). The legacy 4ESS instead required more than 100 equipment bays and up to 5,000 square feet.

"This transition helps AT&T continue supporting long-distance voice services while reducing reliance on aging equipment and preparing the network for the future. This work is part of AT&T’s broader transformation toward a fully IP-enabled fiber network by 2029," added Anthony.

AT&T pointed out that its final 4ESS was located in Alaska, due to the remote nature of the state and the importance of maintaining dependable connectivity across the state. Ironically, Alaska's official nickname is 'The Final Frontier.'

Between 2021 and 2025, the carrier has invested more than $200 million in its network in Alaska.

"The 4ESS helped build the foundation for long-distance communication as we knew it. Its retirement marks the end of an important chapter in history and reflects how our network continues to evolve," said Anthony.

The end of this legacy network infrastructure comes as AT&T continues to ramp up the retirement of its copper network. AT&T plans to retire its copper network by 2029, and has previously signed a deal to sell more than 70 of its copper network Central Offices in an $850 million sale-leaseback deal.