McKenzie, 18, played collegiate soccer at Wake Forest in 2017. The Union academy product has experience at the professional level, having played for the Union's USL team Bethlehem Steel FC the last two seasons as an amateur player.
“We’re delighted to have Mark begin his professional career by joining us as a Homegrown Player this season,” said Union sporting director Earnie Stewart in a statement. “Mark is a promising center back who made an impact for Wake Forest last year, a very good team at the collegiate level. It’s special any time you sign a Homegrown, and Mark is no exception. In this case, he made a difficult decision to leave school to sign with us, and we don’t take that lightly. We look forward to helping him with his development as he takes the next step with the Union.”
A US youth international, McKenzie was a U.S. Soccer Development Academy East Conference Best XI selection at the U-18 level for the 2017-18 season.