Born in Texas, McElreath began racing in 1945 at the age of seventeen, running stock cars on the Dallas area circuits while earning his living as a bricklayer. He spent the next fifteen years racing in local Texas bullrings, building his skills before making a decisive move northward in 1960. That year he and fellow Texan Johnny Rutherford decided to seek out more competitive fields in the Midwest, both eventually securing rides in super modified competition through the International Motor Contest Association (IMCA).
McElreath's talent became apparent quickly. By late summer 1961, his performances had drawn the attention of renowned car owner Lindsey Hopkins, who offered him a ride in the Hoosier Hundred at the Indiana State Fairgrounds on the USAC National Championship Trail. McElreath finished third on his first major open-wheel start, an impressive debut that opened the door to a full career at the top level of American single-seater competition.
McElreath competed across 178 combined career starts in the 1961 through 1983 seasons, recording 48 top-five finishes and five victories. His championship standing results were particularly strong: he finished third in the USAC Championship in 1963 and 1965, runner-up in 1966, and third again in 1970, marking him as one of the more consistently competitive drivers of that era without ever claiming the title.
He made fifteen Indianapolis 500 starts, qualifying for the race in 1962, 1963, 1964, 1965, 1966, 1967, 1968, 1969, 1970, 1973, 1974, 1977, 1978, 1979, and 1980. In 1962, his sixth-place finish earned him the Indianapolis 500 Rookie of the Year award, recognizing his measured and effective debut at the Brickyard.
The highlight of McElreath's career came on September 6, 1970, when he won the inaugural California 500 at Ontario Motor Speedway. He drove a spare car owned by A. J. Foyt and fought a battle with Art Pollard over the final ten laps after both Al Unser and Cale Yarborough retired with mechanical problems. The victory at one of America's premier road courses made McElreath part of motorsport history as the first winner of a race that aimed to rival Indianapolis itself in prestige.
McElreath's career was shadowed by personal loss. His son James Jr. was killed in a sprint car crash at Winchester Speedway in October 1977. That same year, James Jr. had attempted to qualify for the Indianapolis 500 alongside his father, the pair trying to become the first father-son combination to make the same Indy field together; the younger McElreath was too slow to make the grid. McElreath's daughter Shirley married racing driver Tony Bettenhausen Jr., and the couple died when their private plane crashed in Kentucky in February 2000.
McElreath was inducted into the National Sprint Car Hall of Fame in 2002, acknowledging his long contribution to American open-wheel racing. His career, which stretched from the grass-roots Texas bullrings of the late 1940s through more than two decades at USAC's highest level, stands as an example of the self-made American racer who built his craft through sustained effort rather than early privilege.