The visitors took the lead through captain Landon Donovan in the 24th minute with the USA star flicking in from inside the area after Juan Pablo Angel’s run was cut down by the Union defence. It was the fifth goal in a row scored for the Galaxy by Donovan.
However, the Union hit back with six minutes remaining when Danny Mwanga pounced on a poor backpass from Sean Franklin before advancing deep into the area and finishing past Donovan Ricketts and a couple of sprawled defenders to level it up.
The draw kept the Galaxy on top of the Western Conference table but they have played five more matches than second-placed Real Salt Lake who are just two point in arrears.
For sophomore club Philadelphia, they now sit second in the East, a point behind conference leaders New York Red Bulls.