The female suspect drove off after the incident, but police caught up with her shortly afterwards and she was detained, Clark County officials said.
It was not clear whether the crash was intentional, an accident or the result of alcohol or drugs, police said. The suspect was being tested for alcohol and controlled substances, officials said.
Antonio Nassar said people scrambled to stop the woman as she drove on the sidewalk.
"The car rolled right in front of me. By the time I looked over to the right, all you could see was (her) driving away, and people were bouncing off the front of the car," Nassar told CNN affiliate KLAS.
"She rode the sidewalk, she came to a stop at the Paris intersection, people are punching into the window. ... She accelerated again and just kept mowing people down."