Celtic were the first British team to win the European Cup and they have been named Scottish champions 42 times.
The Union have not even played 42 games in their history.
But that did not matter tonight as French midfielder Sebastien Le Toux scored for all important goal for Philadelphia in the 23rd minute.
Celtic did control the game for most of the match and had one goal disallowed, with another chance, the last shot of the game, hitting the crossbar before Union keeper Brian Perk was able to grab the ball as the whistle sounded to end the game.
Perk was tremendous second half in net, denying Celtic on numerous occasions to keep the home side in the lead. After Toni Stahl received his second yellow card and subsequent ejection, Celtic pressed hard for a late goal but came up empty in large part because of the rookie goalkeeper out of UCLA.
“Overall I thought we played very well in the first half, moved the ball well, had a balanced attack, good mobility, and created a number of chances,” said Union coach John Hackworth. “We got a goal and limited the opportunities we allowed Celtic to have, which is good. I think we controlled the tempo and the rhythm of the game, and that was good.”