In the 1972 AFC Playoffs, Harris was on the receiving end of the "Immaculate Reception," one of the most famous plays in sports history. When a pass from Terry Bradshaw bounced off a defender, Harris snatched it out of the air and charged 42 yards to the end zone in the final seconds for a Steelers victory. The play gave the Steelers their first-ever playoff win, a 13-7 victory over the Oakland Raiders.

Harris was chosen for nine consecutive Pro Bowls, from 1972 to 1980 and was All-Pro in 1977. Harris was a key component in the four Steelers Super Bowl championships won in 1974, 1975, 1978, and 1979. In Super Bowl IX, when the Steelers won their first-ever league title with a 16-6 victory over Minnesota, Harris rushed for 158 yards, compared to just 17 yards rushing for the entire Viking team. He was named the game's Most Valuable Player.

Harris played for the Steelers until 1983 and spent his final season with the Seattle Seahawks. He retired with 12,120 rushing yards, 2,287 receiving yards and 100 touchdowns. Harris was elected to the National Italian American Sports Hall of Fame in 1988 and the National Football Hall of Fame in 1990.

Following his retirement, Harris purchased Super Bakery in Pittsburgh. The company, known as "The Leader in Bakery Nutrition," markets its "Super Donuts" and "Super Buns" to school systems in all 50 states. The "Super" products are fortified with minerals, vitamins and protein and are especially popular with students. Super Bakery is a longtime supporter of the National Multiple Sclerosis Society's MS Walk, donating thousands of Super Donuts to walks around the nation to ensure the walkers start they day off with a healthy breakfast.

In 1996, Harris purchased Parks Sausages, a Baltimore-based company rich in history and tradition. Located in a depressed neighborhood in Baltimore, Parks Sausage was the first African-American-owned company in the U.S. to be publicly traded. Franco's purchase and operation of the business rescued and generated a number of jobs for the community. Harris' corporate achievements are chiefly due to his hands-on approach to management, from the boardroom to the manufacturing floor to the marketplace.

Throughout his careers, Harris has been very involved in community service and has received numerous honors and recognition. He is a recipient of the "Whizzer" White Humanitarian Award, The New York Association of the Blind Humanitarian Award, The American Academy of Achievement "Golden Plate Award", the New Vectors' David L. Lawrence Award and the National Urban League's Whitney M. Young Award. In 2005, Franco was a recipient of the First Annual OT 10 Awards for Community Impact. The awards are presented by OverTime Magazine and recognize athletes who contribute unyielding support through community service, charitable donations and entrepreneurial business endeavors.