Blackmon played for
Premier Development League sides
Orange County SC U-23 and
Burlingame Dragons in 2016 and 2017, respectively. He signed with the club on February 22, 2018. Blackmon made his professional debut on March 4, 2018, as an 80th-minute substitute during a 1–0 win over
Seattle Sounders FC. On May 24, 2019, at
Banc of California Stadium, in a 4–2 win over the
Montreal Impact, Blackmon scored his first professional goal on a header in the fifty-fifth minute. On December 14, 2021, Blackmon was selected by
Charlotte FC in the
2021 MLS Expansion Draft, before being immediately traded to
Vancouver Whitecaps FC in exchange for $475,000 of General Allocation Money. On July 26, 2022, Blackmon scored the winning penalty kick for Vancouver against
Toronto FC in the
Canadian Championship Final. On April 9, 2025, Blackmon scored a dramatic late equalizer against
UNAM sending the Vancouver Whitecaps to the semi final of the
2025 CONCACAF Champions Cup. On October 28, Blackmon was named 2025 MLS Defender of the Year. Blackmon contributed two goals and one assist and was an integral part of the second-best defense in the league, which helped Vancouver Whitecaps to their best season, during which they recorded their best points total, most total league wins, their best goal differential, and total goals scored. ==International career==