The largest high school football program in Texas — and one of the nation's most prominent — just became the biggest head coaching vacancy in America.

Allen Eagles coach Terry Gambill announced his retirement on Tuesday after five seasons, according to Greg Riddle of The Dallas Morning News.

Gambill’s half-decade run at Allen comes to a close with a 65-4 record over those five seasons, including guiding the Eagles to the 2017 Class 6A Division I state championship with an undefeated record. Prior to his arrival at Allen in 2016, Gambill accumulated a 67-13 mark at Hewitt Midway over six seasons, highlighed by the Panthers' run to the 2011 4A Division I state championship game.

The move creates a vacancy at one of the most high-profile high school football programs in America, at the largest school in Texas — Allen boasts an enrollment of 6,959 students, 1,379 more than the second-largest school in the state, rival Plano East. The Eagles won five state championships since 2008, including three in a row from 2012-2014 with quarterback Kyler Murray.

Whomever assumes the head coaching job will become the Eagles' fifth coach in the last 25 years, following current Hawaii coach Todd Graham (1995-2000), current Texas High School Coaches Association executive director Joe Martin (2001-03), current Barbers Hill coach Tom Westerberg (2004-15), and Gambill (2015-20).

Stay tuned to TexasFootball.com for more as this story develops.