"Cars were passing by having to avoid it, and almost hitting the horse," said Police Chief Brad Gregg.
He said DUI charges can apply even when the vehicle has four legs instead of wheels.
Police in the northeast Alabama town received a call around midnight Saturday about someone riding a horse on a city street, Gregg said.
Officer John Seals found Melissa Byrum York, 40, of Henagar on horseback on a nearby road and attempted to stop her. Seals asked the woman repeatedly to get off the horse, but she kept trying to kick the animal to make it run, the chief said.
"She wouldn't stop. She kept riding the horse and going on," Gregg said.
After ramming the police car with the horse and riding away, the woman tried to jump off but caught her foot in a stirrup, Gregg said. The officer took the woman into custody and discovered that she had crystal methamphetamine, a small amount of marijuana, pills and a small pipe, the chief said.
York was charged with DUI for allegedly riding the horse under the influence of a controlled substance. She was also charged with drug possession, possession of drug paraphernalia, resisting arrest, assault, attempting to elude police and cruelty to animals.
Gregg said the horse, which belonged to York, "wasn't in the best of health, but it's still alive."