when was University of Virginia last ranked number 1 in the country
1999. 11th ranked Spartans defeated the 4th ranked Wolverines 34-31 in East Lansing.
2007, going into the Ohio State game... after losing by a field goal we dropped to 5th and Ohio State went on to play Florida
Penn State was last ranked in football during the 2011 football season. During Week 14, the last poll prior to the bowl season and the following "Final" polls, Penn State was ranked in both the AP (No. 24) and Coaches' (No. 23) polls. After losing their bowl game, the Nittany Lions were unranked in both final polls.
It has happened six times: 1951, 1952, 1955, 1957, 1965, and 1966. So, 1966 was the last.