The crash happened just after 9 p.m. near the intersection at 6th Avenue and Denny Way near the Seattle Center.
Police say a man driving a white BMW crashed into an SUV, then continued on, hitting a baby in a stroller on the sidewalk before slamming into two parked cars.
The baby was taken by medics to Harborview Medical Center in stable condition. The baby's mother was also taken to the hospital to be treated for minor scrapes and bruises, according to police.
Katie Conover witnessed the crash and was nearly hit by the BMW.
"The car went directly in front of us," she said. "So out of control that we thought maybe the driver had had a heart attack. We didn't know what was going on."
Conover said it looked like the baby was bleeding from his forehead, but didn't appear to be seriously injured.
"Had they been walking one more foot, they would have nailed the stroller," Conover said. "They hit one tire and the baby fell out. It could have been so much worse."
Police say the driver is a suspected drug dealer who was nearly arrested earlier Thursday night. West Precinct Anti Crime Team officers were conducting an operation in the 400 block of Battery Street prior to the crash when they spotted a man believed to be dealing drugs.
The officers tried to arrest the man, but he got away on foot and hopped into a waiting car. Police say the suspected drug dealer is the same man who caused the crash at 6th and Denny,
He fled on foot after the crash, but was found and arrested at about 11:30 p.m. near the Seattle Center, police said.
A stretch of Denny Way near the crash scene was blocked for hours while police investigated, but has now reopened.
The crash was the second serious hit-and-run in Seattle on Thursday. Police say a truck driver hit and killed a woman on First Hill at about 3:30 p.m. That driver has yet to be apprehended.