Prosecutors say the Rio School District trustee began abusing the girl in 2005 when she was 10 years old. The girl is now 15.
Last November she gave birth to a child which was put up for adoption. Martin was accused by his wife of fathering the child. His wife has filed for divorce.
The sex abuse victim was the oldest of four siblings the couple took in when they were abandoned by a distant relative.
School district officials say they reported suspected abuse two years before Martin was arrested. However, police say they could not take action because the girl denied any kind of relationship.
Martin's attorney claims his client is remorseful and wants to counsel other prisoners about how to avoid re-offending.