Roy Chamberlin, 29, would regularly sneak into the woman's house after her husband left for work, then rape her, police said.
Most of the alleged assaults took place at her home in the rural borough of Centre Hall, near State College, and occurred up to three or four times a week, sometimes twice a day, police said.
"She was terrified of Chamberlin," a police complaint said. "Chamberlin always told her to never tell (her husband) or to ever call the police."
Chamberlin threatened to cause the woman "bodily harm" if she ever spoke up, Trooper James Ellis said in an interview.
"He took advantage of the fact that she was not a very strong person," he said.
Fearing for her safety, the woman did not come forward and talk to police until after Chamberlin was charged in another crime and she knew he would be in jail, authorities said.
Chamberlin was unemployed and lived with his parents in Centre Hall. He was in jail in an unrelated case when police in December filed 1,100 counts against him in connection with the alleged sexual assaults, including 183 counts of rape.
Police said he first assaulted her in August 2006 while dating her sister, and that the alleged attacks did not end until September.
His court-appointed attorney, Charles Kroboth Jr., declined comment Wednesday.
Chamberlin was jailed on Oct. 1 on a charge of attempted murder and multiple counts of arson, accused of setting fire to a mobile home on two occasions after arguing with the trailer's occupants.
Police found him at the woman's nearby home while investigating the second fire.
Assistant District Attorney Lance Marshall told the Centre Daily Times she was afraid to come forward until Chamberlin was in jail, "so she didn't tell anyone."
When she finally did talk with police, she said one alleged assault occurred just nine days after she had undergone surgery. She went to the emergency room and was treated for a bruised chest.
The woman's husband told police he saw bruises on his wife about two dozen times and arrived home early one day in June to find her yelling at Chamberlin with the door locked.
Confronted by her husband, the woman declined to discuss the encounter, and her husband said he dropped the issue because of his wife's ailing health, police said.
The husband said he also confronted his wife after an encounter at Chamberlin's house, but the woman again declined to talk about it.
