Hundreds of thousands of bikers converged at the massive Sturgis Rally, one of the biggest gatherings during the pandemic. Mapping their phone data shows where they traveled across the US.

• Hundreds of thousands of bikers converged in Sturgis, South Dakota, in the first week of August for a massive annual rally. It was one of the biggest public gatherings in the US since the COVID-19 outbreak.
• Newly released phone location data shows where people traveled to attend the rally. The data shows people converging from much of the US — especially the Midwest and the South — including Texas, Georgia, and Arizona.
• Over the past week, there has been an average of 100 new COVID-19 cases per day in South Dakota, a rate that has steadily risen since last month.

As COVID-19 cases continue to rise in the US, hundreds of thousands of bikers traveled to a massive annual rally earlier this month in Sturgis, South Dakota, where public health officials have not implemented a lockdown or required people to wear masks.

Newly published phone location data shows that the rally brought people together from all corners of the US, especially the Midwest and the South. Hundreds of thousands of people traveled to Sturgis from states currently experiencing COVID-19 outbreaks, including Arizona, Texas, and Georgia.

Data aggregated by location data firm X-Mode Social shows tens of thousands of mobile devices that arrived in Sturgis in the first week of August, excluding devices that were already active in the area in the months before the rally. In a video published on Twitter, data-visualization group Tectonix GEO mapped the movement of phones across the US that were present at the rally.

Location data companies like X-Mode Social track the precise location of smartphones across the globe using software built into apps that people download. The practice has drawn backlash from privacy advocates, but location data firms and their partners insist that people's movements are anonymized and not directly tied to their identities.

It's not yet clear whether the Sturgis rally, which organizers expected to draw 250,000 people in total, has had any public health effects amid the COVID-19 pandemic. But social distancing and mask-wearing were relatively sparse at the rally, according to The New York Times.

"We are allowed to make our own choices," one rally attendee told The Times. "If we get it, we chose to be here."