context: The Patriots current coach, Bill Belichick, was hired in 2000, and a new home field, Gillette Stadium, was opened in 2002 NFL season. Under Belichick, the team won three Super Bowls in four years (2001, 2003, and 2004). The Patriots finished the 2007 NFL season with a perfect 16-0 record, becoming only the fourth team in league history to go undefeated in the regular season, and the only one since the league expanded its regular season (NFL) schedule to 16 games. After advancing to Super Bowl XLII, the teams fourth Super Bowl in seven years, the Patriots were defeated by the 2007 New York Giants season to end their bid for a 19-0 season. With the loss, the Patriots ended the year at 18-1, becoming only one of three teams to go 18-1 along with the 1984 San Francisco 49ers season and the 1985 Chicago Bears season. The Patriots returned to the Super Bowl in 2012 but lost again to the 2011 New York Giants season, 21-17. In 2015, they won Super Bowl XLIX, defeating the 2014 Seattle Seahawks season by a score of 28-24. The Patriots became the first team to reach nine Super Bowls in the 2016-17 NFL playoffs and faced the Atlanta Falcons in Super Bowl LI, which ended up paving the way for their fifth Super Bowl victory, tying them with the Dallas Cowboys and the San Francisco 49ers for the second-most in NFL history, 1 behind the Pittsburgh Steelers with 6; the game was also the first Super Bowl to go into overtime.
question: Before the year 2007, which teams had ended a year 18-1?
answer: 1984 San Francisco 49ers