The GOAT: the Greatest Of All Time. That's really all that needs to be said about Carmichael. In 1996, he concluded a record-setting run in the amateur ranks by capturing his ninth AMA Amateur National Championship at the prestigious Loretta Lynn's Dude Ranch. He accumulated a total of 67 amateur motocross national championships. He got his first taste of professional motocross in 1996, showing signs of his upcoming greatness, and earned the AMA Motocross Rookie of the Year award. He didn't slow down in 1997, earning a few Eastern Region 125cc Supercross race wins, as well as dominating the 125cc National Motocross Championship Series aboard his Pro Circuit Kawasaki, capturing his first professional championship.
The following year saw much of the same from Carmichael. He won every round of the 125cc Eastern Region Supercross championship and won the 125cc Mazda Truck Motocross National championship with eight overall wins. Carmichael entered the AMA 250cc Supercross Series for the first time in his career in 1999, but had a tough time getting acclimated to the bigger bike and tougher competition. He returned to the 125cc bike for the AMA Motocross Nationals and won his third consecutive championship in the class, his final championship for Mitch Payton's Pro Circuit Kawasaki team.
Carmichael rode a 250cc machine for the entirety of the 2000 season. He earned his first 250cc Supercross win at Daytona and had an additional five podium finishes. Always a stronger outdoor rider, Carmichael immediately dominated the AMA 250cc U.S. Motocross Championship, winning nine overalls and easily winning the series championship. He was a key part of the Motocross des Nations team, bringing the title back to the U.S. alongside teammates Ryan Hughes and Travis Pastrana. Carmichael only added to his stellar career in 2001. After adding a new trainer to his program, he was able to dethrone Jeremy McGrath as the AMA 250cc Supercross Champion, and once again captured the 250cc Motocross Championship aboard his Team Chevy Trucks Kawasaki.
In 2002, Carmichael switched to Team Honda before dominating the AMA Supercross Championship, and set a record that can never be broken in AMA 250cc National Motocross racing: he won every moto he entered that season, going 24 for 24, and earning the first perfect season in U.S. motocross history. The 2003 season saw Carmichael once again win both the AMA Supercross championship as well as the AMA National Motocross championship. In his final season aboard a Factory American Honda in 2004, Carmichael matched his perfect season in the AMA Motocross National series, once again winning all 24 motos of the season, but this time on a four-stroke CRF450R, instead of the two-stroke CR250R two years previous.
Carmichael made the switch to the Factory Makita Suzuki team for the 2005 season. He once again controlled every series that season, winning both the AMA Supercross and Motocross championships, along with the U.S. Open of Supercross and the Motocross des Nations. The 2006 season marked Carmichael's last full year of motocross racing before stepping into semi, and then full, retirement. He once again won the AMA Supercross and Motocross championships, and again captained Team USA to another Motocross des Nations victory. The AMA recognized his achievements by naming him the Athlete of the Year for a record fifth time.
Carmichael went into semi-retirement in 2007, but was arguably still the fastest rider on the track in the races he entered, including winning all six overalls in the six AMA Motocross Championship races he entered. Those six wins brought his combined SX/MX career win total to a record 150. He bid farewell to professional motocross racing by leading Team USA to another Motocross des Nations victory in Budds Creek, Maryland and winning the final race he entered.