Javier 'Chicharito' Hernandez scored twice for the Galaxy in a 3-3 draw with Minnesota United on Decision Day, but RSL's last-gasp 1-0 win over Sporting Kansas City changed the landscape of the Western Conference.
RSL pipped the Galaxy – without post-season football for the second straight campaign – to the seventh and final play-off spot on victories for the season via a 95th-minute winner, having finished level on 48 points at the end of 34 rounds.
Minnesota finished fifth to clinch a post-season berth in the west, along with sixth-placed Vancouver Whitecaps, who drew 1-1 against Seattle Sounders.
Seattle's stalemate and Sporting KC's late loss allowed Colorado Rapids to secure top seed in the Western Conference following a 5-2 rout of Los Angeles FC, who were eliminated as a result.
In the Eastern Conference, Orlando City beat Montreal 2-0 for a spot in the play-offs, along with Atlanta United (2-1 over FC Cincinnati) and New York Red Bulls – the latter using a 1-1 draw against Nashville to extend its post-season streak to 12 years.
Supporters' Shield winner New England Revolution lost 1-0 to already eliminated Inter Miami, Portland Timbers eased past lowly Austin 3-0, DC United defeated Toronto 3-1, 10-man New York City drew 1-1 with Philadelphia Union and reigning champion Columbus Crew – which will not defend its title – beat Chicago Fire 2-0.
Chris Wondolowski scored in the San Jose Earthquakes' 1-1 draw against Dallas before the league's all-time leading scorer announced his retirement.