The crash was east of Sioux Falls and between Sioux Falls and Rowena.
A state trooper said 59-year old Natalie Plueger, of Rock Valley, died when her suburban went off the road and crashed into the Red Rock Bar and Grill.
The initial investigation indicates she experienced medical problems.
Plueger was driving westbound on Highway 42 and veered off to the left and hit the Red Rock Bar and Grill.
She was found unconscious inside her vehicle. There were no skid marks or signs she tried to use her brakes.
A worker inside the bar said the wheels were still spinning when he went outside to see what had happened.
He did not see the crash while he was working in the kitchen, but a loud noise was enough to get Red Rock Bar and Grill employee Bill Shook's attention.
"A lot of times they dynamite next door for the quarry, so at first I thought that. Then, Gloria, the bartender, opened the door and said, 'Oh my God,'" Shook said.
Shook says he went outside right away and found a tan SUV. He did not find any signs she had tried to stop from crashing.
"It looked like she had a heart attack or something," Shook said.
The SUV hit the northeastern corner near the main entrance and a parked car in the parking lot.
"The steering wheel had her pinned in. We didn't touch her. The guys next door are EMTs and they came over. So, they were right on the scene. The accident happened and it probably wasn't four minutes and they were here," Shook said.
There's no sign of visible damage inside of the bar. But the force of the crash was enough to move this jukebox from the corner.
"If she would have hit head-on at the flat side, but she hit right at the corner and that kind of pushed things back in," Shook said.
Shook did not know the woman, but says her license plates were from Iowa.
"Probably on her way to Sioux Falls to go shopping for Christmas; it's just sad," Shook said.
Several area emergency responders were called to the scene including, the Minnehaha County Sheriff, Sioux Falls Fire Rescue, Med-Star Ambulance, and Brandon Police.
This article has been revised to reflect the following correction:
A misspelling was corrected in this story.