Walker Zimmerman scored a stunning 92nd-minute winner to see LA edge a 10-man Real Salt Lake 2-1 at Banc of California Stadium.
The result saw Bob Bradley's side move to 10 points from four games this season, putting it top.
The visitors took the lead in the 35th minute through Damir Kreilach, who sent Tyler Miller the wrong way from the penalty spot.
But Diego Rossi pulled the hosts level before half-time and their chances were boosted when Justin Portillo was sent off in the 84th minute.
It took something special to secure the three points, Zimmerman's spectacular 25-yard effort lifting LA to a dramatic win.
Elsewhere, David Accam's brace helped Philadelphia Union hand Columbus Crew its first loss with a 3-0 victory.
Orlando City edged New York Red Bulls 1-0 and FC Dallas recorded a hard-fought 2-1 win over Colorado Rapids.