How it unfolded
Boston led the series 3–0 and stood one win from a first title since 1941. The game became a brawl by other means: St. Louis led three separate times and Boston tied it each time, 3–3 after regulation. Forty seconds into overtime, Bobby Orr took a pass from Derek Sanderson at the right boards, drove the net, and beat Glenn Hall as Noel Picard tripped him. Orr flew parallel to the ice, arms spread — Ray Lussier's photograph became the sport's most reproduced image. Orr that season became the only defenceman to win the Art Ross with 120 points, plus the Hart, Norris, and Conn Smythe — four major trophies in one year. St. Louis, an expansion-only Western Division representative, reached three straight Finals and lost all three in four-game sweeps.
Why it still matters
Orr's goal outlived the result as symbol. A defenceman ending a series on a rush redefined the position and launched the offensive blue-liner lineage from Paul Coffey to Cale Makar. The sweep also exposed how wide the post-1967 expansion gap had become and pushed the league toward structural reform.