Reto Ziegler put in a header off a set piece in the 25th minute, Roland Lamah scored in the 51st, and FC Dallas (7-1-5, 26 points) withstood intense pressure from LAFC (6-4-3, 21 points) on a hot Saturday evening to get a 2-1 victory and vault into first place.
Both sides spent the first 25 minutes feeling each other out, with LAFC frequently trying to isolate Diego Rossi down the left wing and FC Dallas stretching the field, but scoring chances were hard to come by.
Rossi got a good opportunity from the left side of the Dallas box in the 23rd minute, but the shot went high.
In the 25th minute, FC Dallas broke through when Ziegler headed in a deflection of a corner kick past LAFC goalkeeper Tyler Miller.
The chances came more frequently for Dallas after that, but Miller was up to the task, turning away a shot by Maxi Urruti and then making a critical save on the ensuing corner when he stopped Matt Hedges' header.
Miller wasn't finished. He stopped another Urruti shot in 41st minute, and made the save on a shot from Santiago Mosquera in the box.
LAFC finished the first half looking ragged and a bit tired, and were definitely missing the four important players out for World Cup duty.
The second half opened with Los Angeles showing a lot more life, but Dallas struck again when Lamah got the second goal for Dallas in the 51st minute off an assist from Ryan Hollingshead, finding a way to squeeze a shot into the back of the net through a crowded box.
LAFC didn't let up, though, and Adama Diomande, who entered the game in the 55th minute, scored on a give-and-go play with Benny Feilhaber in the 61st minute to cut the lead in half, aided by some sloppy play from a lethargic Dallas defense.
Diomande almost got a second goal in the 63rd minute off a through ball from Mark-Anthony Kaye, but Dallas goalkeeper Jesse Gonzalez made the save to preserve the Dallas lead in the face of mounting pressure from LAFC.
LA went a man down when defender Jordan Harvey was sent off in the 89th minute after his second yellow card, and though they continued to press for the equalizer, Dallas was able to hold on and get an elusive home victory.