Commonly referred to as simply John Henry, an allusion to the folk hero of the same name,[1] Johnson was a tough and tenacious player who performed at a high level well into the tail end of his career.

After playing college football for St. Mary's Gaels and Arizona State Sun Devils, Johnson was selected in the second round of the 1953 NFL draft by the Steelers, the 18th overall pick.

He instead played one season of Canadian football for the Stampeders, in which he won the Jeff Nicklin Memorial Trophy as the league's most valuable player.

He is the second oldest player to record a 1,000-yard rushing season (behind only John Riggins), having achieved that mark for the final time on December 6, 1964, at the age of 35 years 12 days.

A four-time Pro Bowl selection, Johnson ranked third on the NFL's all-time rushing yards list when he retired, but was best remembered by his peers for the mark he left with his blocking.

[5][6] As a senior at Arizona State in 1952, he played left halfback and was recognized as one of the roughest and hardest runners in the country,[7] and as one of the top defensive players as a safety.

Selected in the second round of the 1953 NFL draft by the Pittsburgh Steelers,[10] Johnson instead played one season in Canada with the Calgary Stampeders of the Western Interprovincial Football Union (WIFU) in 1953.

[17] Johnson earned second-team All-Pro honors from United Press International (UPI) and the New York Daily News.

[18] For the remainder of his time in San Francisco, Johnson was unable to replicate the success of his rookie year, as his production dropped significantly in the following two seasons.

[21] In the 1957 NFL Championship Game, which was won by the Lions 59–14 over the Cleveland Browns, Johnson carried seven times for 34 yards, caught a 16-yard pass, and recovered a fumble on defense.

[23] However, Johnson missed several games due to injuries, and the Lions finished with a 4–7–1 record and one of the league's worst rushing offenses.

[24] In 1959, Johnson was suspended indefinitely by the Lions after he missed the team plane back to Detroit following a one-sided 33–7 loss to the 49ers on November 1 in which he carried the ball five times for only eight yards.

[25][26] To that point, the Lions had a 1–5 record, and coach George Wilson used Johnson's suspension as an opportunity to call out the team for its lack of "desire.

[21] He made three straight Pro Bowl appearances, and was a second-team All-Pro selection by the AP, UPI, and Newspaper Enterprise Association in 1962.

[33] It was only the ninth 200-yard rushing game in NFL history to that point, and the performance made him the oldest player to reach that mark, a record he still holds.

[33] After playing out his option with the Steelers, in July 1966 Johnson signed as a free agent with the Houston Oilers of the American Football League.

As of 2023, he is fifth on the Steelers franchise all-time rushing yards list, behind Franco Harris, Jerome Bettis, Willie Parker, and Le'Veon Bell.

[49] In November 1955, while on the sick list for the 49ers due to a shoulder injury, Johnson carried two women to safety out of a blazing apartment building in Oakland, California.

[19] The couple divorced in 1959, and a bench warrant was issued for Johnson after he fell $2,360 behind on alimony payments, concurrent with his suspension from the Lions for missing the team plane.

[21][50] Several days later, it was announced that Johnson and his fellow Million Dollar Backfield teammate, Joe Perry, who died six weeks earlier, would have their brains examined by researchers at Boston University, who were studying head injuries in sports.