Gary Rolls, 47, faces at most a year in jail as part of a deal with prosecutors. He pleaded guilty Tuesday to illegal use of a computer, tampering with evidence and fourth-degree criminal sexual conduct.
Rolls had been scheduled to stand trial next month on four counts of first-degree criminal sexual conduct, charges that carry a maximum penalty of life in prison.
Rolls was accused of having sex with a girl with whom he began a relationship when she was 9. The woman is now in her 20s.
Defense lawyer Jeffrey O'Hara said the woman lied about numerous details.
Rolls, who resigned his county commission seat, is scheduled to be sentenced June 19.