At least one person was killed and 37 others injured near the Paris Las Vegas Hotel on Sunday night, authorities said.
Witnesses said the woman was driving down the Strip before her car jumped onto the sidewalk and started striking pedestrians.
She allegedly returned to the sidewalk at different spots and hit more people before barreling down the road.
Police arrested the driver, and she is undergoing tests for alcohol and controlled substances. A 3-year-old in the car with her was unharmed.
Authorities ruled out terrorism, saying an initial investigation shows the driver did it deliberately.
"This was not an act of terrorism," Deputy Police Chief Brett Zimmerman said. "We are treating this as an intentional act."
The driver, who is in her 20s, went on the sidewalk at least three or four times, according to Zimmerman.
Homicide division officials are looking at numerous surveillance videos from the Strip.
'She just kept mowing people down'
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."
Rows of ambulances and police cars gathered at the scene, their lights flickering.
"If anyone is still in the area who witnessed the crash, please find an officer on scene, we'd like to get a statement from you," the Las Vegas Metropolitan Police Department tweeted.
'She was looking straight forward'
Witnesses described disturbing scenes as crowds fled.
"Everyone was running ... and as I was running, I saw a car up on the sidewalk coming toward us," a witness told the affiliate. "I saw a lady ... she didn't seem like she wanted to stop the car, she had both hands on her wheel and she was looking straight forward."
Others tried to stop the driver and drag the toddler out, she said.
"I saw men running after her, yelling, 'stop, stop!' As she was passing, we saw people running after her. Everyone was so frantic and just running around."
Traffic snaked down the streets as cars were diverted near the Paris Las Vegas Hotel.
The Las Vegas Strip is lined with luxury hotels and casinos, and is filled with revelers taking in the neon lights on any given night.
Shortly after the crash, the Strip emptied, an unfamiliar sight in the heart of the vibrant city.