A study conducted by the Seattle mayor's office found Portland has the second-lowest rate of COVID-19 cases per capita of the nation's 30 largest cities—behind only Seattle.

Multnomah County has seen 8.9 infections per 1,000 people. That rate is just above Seattle's 7.4 cases per 1,000.

The data isn't exact, concedes Seattle Mayor Jenny Durkan. For one thing, there's no easy way to compare Portland and Seattle directly, since infection rates are kept only for Multnomah County, not for areas strictly within city limits.

Still, the results are striking. Nashville, the city with the highest per capita caseload in the country, has seen 41.8 people sickened per 1,000—five times the rate of Portland. Rounding out the top five? El Paso, Memphis, Phoenix and Houston.

Durkan's office says it conducted the study with no idea Seattle would finish on top.

"It's the people of Seattle who have kept the case count low, by being serious about social distancing, about hygiene and washing your hands, about wearing face covers, and about getting tested," Durkan's chief of staff, Stephanie Formas, told the Times. "Seattle has made the commitment to protect our neighbors and to protect ourselves from the spread of COVID."

It's not immediately clear why Pacific Northwest cities have fared so well—especially since the COVID-19 virus first landed on the Pacific coast. But Oregon and Washington officials both acted comparatively swiftly to shut their states down when the pandemic began and have reopened only gradually. In Portland, mask wearing has not become a matter of partisan debate—it's common practice.

One interesting note: Seattle and Portland maintain their low rates of COVID-19 infection despite being the U.S. cities where protests against police violence have had the most stamina. The demonstrations simply don't seem to have spread the virus.

Correction: Due to an error by the Seattle mayor's office, this story initially said Las Vegas had the highest infection rate in the country, at 76.7 per 1,000 people. In fact, Las Vegas ranks eighth, with 29.9 infections per 1,000 people.