The Steelers are the only NFL team that sports their logo on only one side of the helmet. At first, this was a temporary measure because the Steelers weren't sure they would like the look of the logo on an all-gold helmet. They wanted to test them before going all-out.
Equipment manager Jack Hart was instructed to put the logo only onthe right side of the helmet. The 1962 Steelers finished 9-5 and became the winningest team in franchise history to date. The team finished second in the Eastern Conference and qualified for the Playoff Bowl. They wanted to do something special for their first postseason game, so they changed the color of their helmets from gold to black, which helped to highlight the new logo.
Because of the interest generated by having the logo on only one side of their helmets and because of their team's new success, the Steelers decided to leave it that way permanently. Today's helmet reflects the way the logo was originally applied and it has never been changed.