The woman, who cannot be named for legal reasons is thought to have the mental capacity of a six or seven year old.
The attack happened on the evening of October 24. The victim was interviewed by deputies on October 25 and 26, and charges were filed against the man.
The man, who is named in some newspaper reports, has been released on a $250,000 bond, and pleaded not guilty to a charge of sexual assault in front of the court on November 21. The next court appearance is set for December 9.