Antenna tower operator Crown Castle International has announced it will buy privately held Lightower Fiber Networks for about $7.1 billion in cash to acquire the company’s extensive fiber assets across the northeastern United States that will be used to connect small cell 5G networks.

The acquisition will allow Crown Castle to market an extensive fiber backhaul network in large cities like New York, Boston, Washington, Chicago, Detroit and Philadelphia, as well as smaller cities particularly in upstate New York, Ohio, Virginia, Pennsylvania, Massachusetts and northern New England. Crown Castle, which already owns many of the cell towers where AT&T and Verizon place their equipment, will now be able to market fiber backhaul connectivity for AT&T and Verizon’s forthcoming 5G networks.

LIghtower’s fiber footprint.

Lightower’s fiber network was originally focused on major markets like Boston, New York City, the District of Columbia, and Chicago. Its partner, Fibertech — acquired by Lightower in 2015, focused on 30 mid-sized cities from Indiana to the west to Maine in the east. The network’s customers are large companies and independent ISPs. In Rochester, where Lightower maintains a Network Operations Center, Greenlight Networks relies on a fiber backhaul network originally built by Fibertech to connect its fiber-to-the-home broadband service. That fiber is likely to soon be shared with AT&T, Verizon, and potentially T-Mobile and Sprint to power any 5G buildouts in the region.

“Lightower’s dense fiber footprint is well-located in top metro markets in the northeast and is well-positioned to facilitate small cell deployments by our customers,” said Crown Castle CEO Jay Brown in a statement. “Following the transaction, we will have approximately 60,000 route miles of fiber with a presence in all of the top 10 and 23 of the top 25 metro markets.”

This acquisition marks Crown Castle’s first major diversion outside of its core market — leasing out the cell towers it owns or acquires.