The Terps ended their nonconference schedule taking down the Golden Flashes on the backs of Taulia Tagovailoa, Tayon Fleet-Davis and Dontay Demus.
The Terps reached 3-0 for the first time since 2016 in pulling out a scrappy, ugly victory over the Fighting Illini.
The kicker nailed the winner in his third attempt of the night from 32 yards out, bringing the Terps to 3-0 for the first time since 2016.
Coach Mike Locksley emphasized the importance of his squad playing to their own standards and not to the opponent.
While the offense failed to finish drives, Jordan Mosley and Lawtez Rogers had standout performances on defense.
The three-star product joins the Terps from nearby St. John's College High School.
Castleberry didn't receive a carry for Michigan last season.
Harrison suffered a season-ending knee injury against Penn State on Sept. 27.
Coach Mike Locksley has focused on building the program's foundation in his first year.