Riggs began racing at fourteen in the American Motorcycle Association, winning the North Carolina State Championship two years running. At seventeen he moved to NASCAR's mini stock division and won twelve races in his first three seasons, eventually becoming a two-time champion at Southern National Speedway. He made his Craftsman Truck Series debut in 1999 at Indianapolis Raceway Park and ran part-time through 2001 with Ultra Motorsports, where he won five races including one at Martinsville and finished fifth in the Truck championship.
In 2002, Riggs moved to the Busch Series to drive the No. 10 Ford for ppc Racing. He won at Nashville Superspeedway and again two weeks later at California to announce himself as a serious series contender, finishing tenth in points and winning Rookie of the Year. In 2003, he added two more wins — a last-lap pass for victory at Gateway after leader Mike Bliss ran out of fuel, and another at Nashville — and finished sixth in the championship with a chance to compete for the title at Homestead before crashing early. He also won the series Most Popular Driver award that year.
Riggs signed with MB2 Motorsports to drive the No. 10 Chevrolet in the Cup Series in 2004, qualifying for all but one race and finishing fifth at Dover with a 29th-place championship result. In 2005, he won his first Cup pole at Martinsville and posted a second-place finish at Michigan. He moved to Evernham Motorsports for 2006 with the No. 10, retaining the Valvoline sponsorship, and produced his best season: a fourth-place finish at the Sharpie 500 at Bristol; a third-place run at Atlanta; wins of both Charlotte poles (Coca-Cola 600 and Bank of America 500); victory in the NEXTEL Open exhibition race at Charlotte, leading all but one lap; and a ninety-lap stint at the front of the Coca-Cola 600 before a pit road violation derailed a potential top-five. He also became the first driver to sweep both Charlotte poles in a season.
Riggs's fortunes declined sharply in 2007 as the team fell out of the top-35 in owners' points, leading to multiple DNQs. He did not renew with Evernham and signed with Haas CNC Racing for 2008, but was released when Tony Stewart arrived and that team became Stewart-Haas Racing. A season with Tommy Baldwin Racing in 2009 produced eight Cup starts before Riggs departed rather than accept a start-and-park role. Subsequent Cup appearances were increasingly sporadic — brief stints with Keyed-Up Motorsports in 2010, Whitney Motorsports in 2011, and Xxxtreme Motorsport in 2013 — and his top-level career effectively wound down through the early 2010s.
Riggs's son Layne Riggs followed him into professional racing and competes in the NASCAR Craftsman Truck Series, driving the No. 34 truck for Front Row Motorsports.
Riggs's career peak — the 2006 Evernham season — demonstrated he was capable of leading large chunks of marquee races and dominating qualifying at the sport's most prestigious tracks. The NEXTEL Open win and the sweep of Charlotte poles in that season stand as tangible evidence of his competitive ceiling. That the equipment subsequently deteriorated around him, rather than his own ability fading, is the defining context of a career that never quite consolidated its mid-decade momentum.