Wake Forest (18-7), which had been ranked No. 23 last week, dropped out of the poll Monday after losses at Virginia Tech and N.C. State.
That left Duke (23-4), which moved up one spot to No. 5, as the only ACC team ranked by The AP.
"Others Receiving Votes" were Virginia Tech (76), Maryland (57), Wake Forest (2) and Clemson (1).
Before Monday, the ACC had always had at least two AP-ranked teams since the rankings expanded from a Top 20 to a Top 25 at the start of the 1989-90 season.
The last time the ACC had just one ranked team was the poll of Dec. 13, 1977, when there were only 20 teams in the rankings.
Both the Big 12 and the Big East lead the current poll with five ranked teams. The Big Ten has four ranked teams, and the SEC has three.