The championship was a long-awaited one for the Blues franchise, which reached the Stanley Cup Final in each of their first three years of existence from 1968-70 but were swept each time, including by the Bruins in 1970.
St. Louis showed it could put a stranglehold on opponents when playing with a lead.
After the game, the Capitals congratulated the Blues on their victory on Twitter. They worked so hard to get to this point.
Stanley Cup champions, at last.
Although no one's comparing him to the Great One, O'Reilly entered the record books alongside Wayne Gretzky after putting the Blues on the board Wednesday with a goal in his fourth straight game.
O'Reilly was awarded the Conn Smythe Trophy as playoff MVP.
"I stopped trying to worry about the outcome and just give it everything I had", said O'Reilly, who scored his team's opening goal in the last four games of the Stanley Cup Final.
'I was getting bounces.
Returning to the site of their last appearance in the final, which ended when Bobby Orr sailed through the air after scoring the Cup victor, the Blues won for the third time in Boston this series and an National Hockey League record-tying 10th time in the post-season. It was just awesome'. Following an uneventful second period, Brayden Schenn and Zach Sanford added insurance goals in the third.
Grzelcyk's return is a major boost on the blue line for Boston.