Sam started his racing career as many drivers have, in karts. Sam began to competitively kart in 1991 at the age of 12. By 1993 Sam had recorded 7 wins and 29 top-five finishes in only 37 starts. Through 1995, Sam had captured an additional 32 victories, including 4 National Championships, and 81 top-five finishes in 113 starts. That is a 100% success rate on finishing in the top-five. Amazing!

In 1996, Sam moved to the F2000 series. Although, Sam didn't record any wins, his time there was still a success. By 1998 Sam had worked his way to 7th overall in the series. From F2000, Sam moved again, this time to the Toyota Atlantic series, however he also qualified for the IRL in testing. 1999 saw Sam capture his first Toyota Atlantic win, and also earn the Rookie of the Year award. In 2000, Sam ran a limited schedule in the IRL. Of the 8 races ran he scored his highest placing of 3rd at Las Vegas.

2001 was the coming of age for young Sam Hornish, Jr. Leading the series from start to finish, Sam dominated with 3 wins, 8 top-five finishes, and 2 top-ten finishes in capturing his first series Championship, becoming the youngest open-wheel champion in North American motorsports history. However the story doesn't end here. 2002 saw Sam continue his winning ways with 10 podium finishes, including 5 wins, and his second consecutive series Championship. The first time that has ever been done.

In 2003 Sam captured 3 more wins but was only able to pull out a 5th place finish overall. Moving to Penske for the 2004 season, Sam earned one win on his way to 7th overall.