The junior held off a late charge from sophomore Abdinasir Hassan (CO), who finished second in 4:01.45, a Colorado No. 1 mark and a new U.S. all-time sophomore record.
Mantecon's time breaks the long-standing U.S. high school indoor mile junior class record of 4:02.21, set in 2012 by Edward Cheserek of St. Benedict's Prep (NJ).
Hassan's runner-up finish was historic in its own right. The sophomore shattered his own previous sophomore best of 4:10.19, while eclipsing the former class record of 4:07.04 by Marcus Reilly (MA) set in 2022 at the Boston University Last Chance Meet.
Mantecon ran a controlled, well-paced, yet aggressive race from the gun, closing with a 56.40.
Mantecon's splits: 61.17, 2:03.23 (62.06), 3:04.26 (61.03), and 4:00.66 (56.40).
The mile victory capped what may go down as one of the greatest three-day championship stretches ever by a U.S. high school distance runner.
Over four days at Nike Indoor Nationals, Mantecon stacked elite performances across four events:
Thursday: Won the 5000m in a meet record 13:57.94, taking over the U.S. No. 1 spot.
Friday: Captured the 2-Mile title in 8:48.02.
Saturday: Anchored the Belen team's 4000 DMR victory, running a 4:04.73 on the anchor leg.
Sunday: Closed his meet with the Championship Mile Title and a U.S. indoor record 4:00.66.
Several athletes also delivered major performances in the loaded championship 1-Mile field.