Born in Delavan, Illinois in 1915, McDowell grew up in Pasadena, California. He began driving big cars at Legion Ascot in 1934 but soon became a regular on the independent circuits of the Pacific Northwest.
Johnny remained with the big cars becoming a star in the Ohio based CSRA circuit. He got his first look at the Indianapolis 500 as Frank Wearne's riding mechanic in 1937.
In 1939 Johnny took on the midget drivers at the famous Gilmore Stadium in Los Angeles. He held the point lead in mid-September eventually finishing 2nd to the great Bob Swanson. John was always at the top of the standings winning a total of 13 features at Gilmore including the 1947 Grand Prix.
He ranks 9th on the all-time winners list at that most difficult of tracks. McDowell placed 2nd in the 1947 AAA West Coast midget standing. In 1948 he shifted his focus to the Midwest where he won at least eight AAA midget features and the 1948 Chicago Soldier Field title. McDowell competed in four 500 Mile Races from 1949-52.
He was killed at Milwaukee, Wisconsin during a National Championship big car race in 1952 at age 37.