Facebook announced today that it will be building its third huge data center facility in the desert in the middle of Oregon. The company intends to invest at least $200 million in this expansion of its site, which is the first of five around the world that Facebook has constructed from the ground up.

“Building 3 will feature the latest Open Compute Project hardware designs — including Yosemite, Wedge, and 6-pack — and, like our other buildings, will be cooled using our cool Central Oregon high desert air instead of energy-intensive air conditioners,” Ken Patchett, director of data center operations for Facebook’s West Region, wrote in a Facebook post today.

In addition to these three buildings in Prineville, Oregon, Facebook also has a cold storage facility for holding onto less frequently accessed data, like old pictures.

Facebook is one of a few web companies that have opted to erect entire buildings to hold their own IT equipment. (Others include Google, which is coincidentally looking to expand its own data center site in Oregon). These days, many modern tech companies rent out access to server and storage hardware in clouds like Amazon Web Services or pay for space for their hardware inside colocation facilities.

Facebook also has data center sites in North Carolina, Iowa, and Sweden. And in July the company confirmed — following speculation — that it would build out its fifth site, in Fort Worth, Texas.

I used to live 40 minutes away from Prineville, in a city called Bend. When I met Patchett a few years ago, when there was just one building on the site, I asked him if Facebook would ever construct another building to run its servers, storage, and networking equipment in the area. He told me it would depend on usage of Facebook.

Back then Facebook had around 750 million monthly active users. Of course, Facebook has since grown a lot. Now it has just about twice as many users — 1.49 billion on June 30. Hence the need to grow the infrastructure footprint, both in Prineville and elsewhere around the world. Patchett’s answer seemed vague to me at the time, but he was right.