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 Angelâ€™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.