Theories over the stunning, mystery lights were many. Witnesses posted their videos on social media asking the burning question: What the heck was that? Was it a meteor? A missile? Evidence of extraterrestrial life?
So far, one theory has gained the most traction: It's a heap of burning space junk.
Witnesses shared their images and videos on social media, as well as their amazement over the sight.
"We saw the most ridiculous fireball in the sky," said Ian Norman, a photographer, in a personal video account of what he saw from the slopes of the Sierra mountains in California.
He shot a video that showed what looked to be two bright, burning streaks flying across the horizon.
Throughout the west, people stepped outside to marvel and capture the lights on camera.
An astronomer at the Havard-Smithsonian Center for Astrophysics chimed in on Twitter with his theory: It's from a Chinese rocket, called the Chang Zheng 7 rocket that launched on June 25.
In response to questions about how he arrived at that conclusion, Jonathan McDowell said he had "looked for objects near reentry" and had calculated ground track versus time, and saw that the Chang Zheng 7 was over Utah at the time.
McDowell's theory is that it's debris from the new generation of Chinese rockets.
China had launched the rocket, also known as the Long March 7, last month to deliver a prototype shuttle into space. Its developers had touted the rocket
as "more environmentally friendly," producing less pollution than previous models.
McDowell's conclusions started gaining more traction online.
But since all this unfurled on the Internet, there was plenty of humor to be found over the mystery.
A parody Superman account tweeted: "No #meteor hit Earth today. You're welcome." Another one showed a smiling Pikachu soaring across space like a meteor (or a chunk of burning space trash).
If you missed the light show don't worry -- you can catch the Delta Aquarids
meteor shower Thursday and Friday night over much of North America.