The Warriors limited Westmoreland, which had rushed for more than 3,000 yards this season, to just 92 yards on the ground.
Senior quarterback Tilton Pickett connected with Zaiden Humphrey for a 39-yard touchdown, and Sam Pickett followed with a 73-yard touchdown run for the Warriors.
Marion County (11-2) will host York Institute (11-2) in next week’s semis. The Dragons defeated Bledsoe County 31-7 in another quarterfinal, ending Bledsoe’s season at 11-2.
Hear the game via the stream on www.theriver1049.com.
Buckner rushed 16 times for 260 yards and a touchdown, while Cooper ran for 127 yards and three touchdowns on 16 carries. The Pirates (11-2) amassed 447 total yards.
The Pirates advanced to the 1A semifinals for the 23rd time and will host Coalfield on Friday, looking to reach the title game for the 15th time.
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By winning its 12th straight game, Sequatchie County (12-1) advances to the state semifinals for the first time since 2016. There, it will host nine-time reigning state champion Alcoa.
The game will be broadcast on Country Roads 93.3.