The defending Olympic Time Trial gold medalist was the last to start of the night, and while she set a blistering pace, Armstrong lost control of her bike on a tight corner at the turnaround point and took a hard fall on her left side.
At a press conference following the race, officials announced that Armstrong was being taken for X-rays, but declined to release her condition, but later her husband told the Idaho Statesman that Armstrong would be out of the rest of the Exergy Tour and was expected to undergo surgery. The Associated Press later reported that Armstrong broke her collar bone in the fall.
While she jumped back up on her bike after the fall, delivering a still very-respectable time of 4:17, Armstrong was visibly shaken and in pain as she dismounted, clutching her shoulder and limping.
Tara Whitten of Team TIBCO finished in first place with a time of 4:09, taking the first-ever leader's jersey. The victory was especially sweet for the team, whose bikes and equipment were stolen from a trailer only one day earlier, only to be recovered by the Boise Police Department later that day.
As Boise Mayor Dave Bieter awarded Whitten her medal, he smiled and added, "I'm so glad you got your bike back."
Gillian Carleton of the Canadian National Team finished second, followed by fellow Canadian Clara Hughes of Team Lululemon in third, both just fractions of a second behind Whittman. Official results were still pending as of Thursday night.
Armstrong's fall was a primary topic for the hometown crowd as well as other racers. After her win, Whitten commented that while the victory is a huge honor, she was sorry to hear about Armstrong's fall.
Crowds who turned out for the event seemed energized and ready to celebrate the return of professional women's cycling to Idaho. Fans lined not only the start and finish point in Julia Davis Park, but the route along Capitol Boulevard to the Boise Train Depot.
Whitten commented on how thrilled the riders were to receive such a welcome and support, yet after Armstrong's fall, the atmosphere among the crowd was visibly deflated.
The tour continues on Friday with Stage One beginning in downtown Nampa at 11 a.m.