Denver came in last place in the latest RootMetrics mobile speed report for the 125 most populated U.S. markets.

That means Denver did worse than Flint, Mich. (which was No. 54), McAllen, Texas (No. 122), and even Colorado Springs (No. 121).

Compared to first-place Atlanta’s 94.1 data score, Denver’s 78.4 showing was pretty awful.

All four major carriers in Denver saw their mobile network speeds drop below 10 mbps during the test period from Feb. 11-18. During that period, RootMetrics sent people to the Denver area to conduct 20,419 tests of mobile network reliability, data speeds and data, voice and text performance.

“All four carriers recorded median download speeds below 10.0 Mbps in Denver, and median upload speeds were even slower. Due in part to the slow speeds, Denver also ranked just No. 124 in data performance. Unfortunately, this isn’t unfamiliar territory for Denver, as the Mile High City was No. 122 in speed No. 121 in data during our previous round of testing,” according to the report.

Being last is a bit of a shock. But we should have expected the low rank after coming in in the bottom five markets for mobile performance earlier this year. At the time, RootMetrics spokeswoman Annette Hamilton said it could be because of Denver’s growing population.

“In general, as carriers add customers, we have seen that networks slow down until the network catches up again. We can’t say for certain that this is or will be happening in Denver, but it is something we have seen in the past,” she said in April.

On Wednesday, Hamilton offered additional insight into how the scores are tabulated. RootMetrics, which buys its own phones at the store to use during tests, looks at a mobile user’s ability to connect and stay connected.

In Denver’s case, she said, two things are happening: network congestion or interference, and mobile carriers performed worse compared to that of other regions.

“But you are not alone,” she said. “In our experience other cities in the Rockies area tend to have challenges when it comes to data performance, and we have yet to be able to pinpoint exactly why this happens. We can note that when it comes to LTE service, the Denver area is fairly saturated, showing that carriers are making efforts to improve their overall network performance in the area. This, in part, could be why we are seeing a slow climb for the city, moving from (overall rank) No. 122 to No. 119.”

While Denver’s overall score for each carrier in the first half of the year was in the low- to mid-90s, RootMetrics found that download speeds dropped from August. Sprint’s median download speed slowed nearly 25 percent to 9.8 mbps. T-Mobile’s dropped to 4.4 mbps, down 35 percent from August’s 6.8 mbps.

By comparison, the speediest city was Atlanta, where Verizon topped median download speeds at 33.3 mbps. Even there T-Mobile saw a decline as well — down to 16.5 mbps from 26.2 mbps in August.

Out of the 125 slots, Denver ranked 84 for reliability, 87 for calls and 64 for texts and a lowly 124 for data performance.

Updated Aug. 3, 2016: This story has been updated to include comments from RootMetrics’ Annette Hamilton.