The ambitious new league's opening match looked set for a shoot-out before Wynalda moved on to Ben Iroha's cross-field pass three minutes from time, beat two defenders inside the penalty area and curled a right-foot shot into the far top corner.
"I can't explain the emotion of scoring the goal. It meant more to me than any goal I've ever scored," a tearful Wynalda said. His tears of joy probably saved the major league's chairman, Alan Rothenberg, from shedding a few of his own in fear and frustration. He was "greatly relieved" the game did not end in a 0-0 draw.
That would have been an anticlimax after the match had been built up before kick-off with typical American hoopla involving hundreds of children, streamers and rock music.
For the first of 160 games, it achieved its goal, but it was less than perfect, with sloppy passing, poor finishing and some rough tackles. "I hope the level of play improves and I'm sure it will," said the United States national team coach, Steve Sampson, who pointed out the teams had only five weeks to prepare together.
Wynalda, who scored a memorable goal for the US in the 1994 World Cup against Switzerland with a swerving free-kick, saw a similar effort in the 66th minute superbly saved by Washington goalkeeper Jeff Causey. Later Wynalda, who used to play in the German Bundesliga, beat Causey with a low diagonal shot but the ball flew inches wide of the far post.
United, led by John Harkes, once of Sheffield Wednesday, Derby and West Ham, seemed to tire in the second half and their Bolivian striker Marco Etcheverry was a major disappointment.