Though the Federal Communications Commission officially closed its doors more than a month ago, due to the U.S. government shutdown, the agency kept enough staff around for a critical 5G development: Auction 101, the sale of 28GHz millimeter wave (mmWave) spectrum licenses covering the United States. After 38 days and 176 rounds of bidding, Auction 101 sold the licenses for just over $700 million — a decent but not amazing sum for the U.S. Treasury.

Auction 101 was important because mmWave is a crucial technology underlying 5G networks (see our 5G Cheat Sheet), but until now, very few companies could legally use that spectrum for communications purposes. In one fell swoop, the auction made an entire country’s worth of high-bandwidth spectrum available to national, regional, and smaller companies, enabling 5G networks to be built by anyone with enough cash to win licenses.

In a nutshell, mmWave promises super-fast data speeds and unprecedented responsiveness, also known as ultra-low latency, which are set to enable everything from wireless home broadband service to untethered VR/AR headsets, remote surgery, and fully autonomous vehicles. Verizon and AT&T anticipated mmWave’s importance years ago, each acquiring obscure companies that held FCC mmWave licenses long before the latest auction. Others had to wait for the auction to stake a claim to spectrum.

While mmWave isn’t the only way to send 5G data, it’s the fastest and most responsive. That’s the key reason Verizon says its “true 5G” network is focused on mmWave hardware, and it largely explains why AT&T’s latest marketing now refers to mmWave as “5G+.” As a fallback, carriers with few or no mmWave licenses plan to offer slower and less responsive 5G service over lower radio frequencies, a decision that has recently led to marketing battles (see: AT&T and T-Mobile) over the meanings of “5G” and “5G Evolution.”

Buying mmWave spectrum before the auction required an expensive leap of faith. Engineers would somehow need to shrink mmWave hardware from satellite dish-sized enclosures down to pocketable devices. A consortium of companies rallied and got the 5G standard approved early, but the mmWave miniaturization process took so much time and effort that regulators around the world weren’t all ready to license millimeter wave spectrum to cellular carriers.

Now virtually any U.S. company can buy a mmWave license. Several of the over 3,000 town/city-sized licenses reportedly sold for as little as $200, with fewer than 200 licenses raising between $1 million and $12.5 million. But a bare bones statement from the FCC has left more questions than answers as to what actually happened. Did any of the major cellular providers purchase additional 28GHz spectrum for 5G? How about cable companies? Any other competitors of possible significance?

As of now, the identities of the winning bidders aren’t known to the public, and they won’t be revealed until the FCC concludes a second millimeter wave auction, Auction 102, focused on nearby 24GHz spectrum licenses. The start date for Auction 102 hasn’t been announced yet — and may well wind up impeded by the shutdown — but it could itself take another month or more to wrap up.

It’s fair to say that what happens with 24GHz and 28GHz mmWave spectrum will determine the evolution of 5G services in the United States, as well as the world. The United States is now in an awkward situation in which two carriers have launched early, spotty 5G networks using chunks of millimeter wave spectrum. And multiple carriers have announced vague plans to expand their 5G footprints using mixes of mmWave and non-mmWave hardware. Whether any carrier has a super-fast nationwide network powered by tons of mmWave “small cells,” or a slower, less responsive network based on older radio technology, depends substantially on the outcome of these auctions.

Auction 101 had the potential to be an international 5G milestone, and history may wind up recording it as such. Unfortunately, we’ll have to wait a while to see who won the auction, what happens with Auction 102, and how widespread any carrier can get with mmWave hardware.