Rathmann was born James Merwin Rathmann, going by the name Jim. When his younger brother wanted to begin racing at an age that would have barred him from entry, the older brother lent his identity to enable the younger's participation. The older brother took the name "Dick" in exchange, and what began as a temporary arrangement became permanent. As a result, Dick Rathmann spent his career under a name that was not legally his own, while his brother Jim — born with the Dick name — went on to win Indianapolis under that alias.
Rathmann began his open-wheel career in the AAA Championship Car series in 1949 and 1950, making four starts including the 1950 Indianapolis 500. His best result in the AAA era came at Milwaukee in 1950, where he finished sixth.
In 1951, Rathmann transitioned to NASCAR's Grand National Series, where he became a successful competitor through 1955. His stock car record established him as a capable front-runner at a time when NASCAR's national series was still defining itself.
Rathmann returned to USAC Championship Car racing in 1956 and competed through 1964, adding 41 starts including appearances at the Indianapolis 500 from 1956 and again from 1958 through 1964. His best open-wheel finish came in 1959 when he placed second at Daytona, and he accumulated 21 top-ten finishes in the USAC era. He qualified for the 1957 Indianapolis 500 but was mugged the night before the race and replaced by Johnnie Parsons.
Rathmann's most consequential moment in racing came at the 1958 Indianapolis 500, where he started from the pole position. On the very first lap, Rathmann and fellow front-row starter Ed Elisian raced aggressively into Turn 3, triggering a chain-reaction accident that involved 15 cars and claimed the life of driver Pat O'Connor. Rathmann completed no laps as a result, making him the first Indianapolis 500 pole-sitter in the race's history to fail to complete a single lap. That distinction has been matched only twice since, by Roberto Guerrero and Scott Sharp.
His participation in the Indianapolis 500 during its years as a round of the FIA World Championship (1950–1960) credited him with five World Championship starts, one pole position, and two World Championship points.
Rathmann was inducted into the West Coast Stock Car Hall of Fame in 2009, recognizing his contributions across NASCAR and American open-wheel competition. His career is inseparable from the remarkable identity story he shared with his brother Jim, whose 1960 Indianapolis 500 victory — won under a borrowed name — gives the Rathmann saga a strange symmetry: both brothers raced and won under names that were not originally theirs. Dick Rathmann's versatility across AAA, USAC, and NASCAR, combined with his role in one of Indianapolis's most dramatic first-lap accidents, cements his place in mid-century American motorsport history.