The point keeps Drogheda in fifth place and keeps alive their hopes of gaining a European place as the season enters its final quarter.
A dull game came to life in the 72nd minute when Graham Gartland was red-carded for handling on the goal-line. Longford took the lead when Barry Ferguson converted the resultant penalty.
Ten-man Drogheda made little impact in trying to get themselves back into the game and the home fans were starting to drift away when a late cross from the right found Stuart Malcolm who squared to Mark Leach and he made no mistake as he blasted home from 15 yards for a 93rd minute equaliser.