The "title cash" office on Montgomery Highway was robbed just before 1 p.m. Saturday afternoon.
Police say a man with a knife demanded money.
The suspect also raped the female clerk before fleeing on foot with an undisclosed amount of cash.
Police hope a composite drawing will help identify the suspect and put him behind bars.
Investigators say the man is in his mid-to-late 40's.
He's about six feet tall and weighs about 200 pounds.
Crimestoppers is offering a reward of up to $1,000 for information that leads to an arrest in the case.