As far as MLS rivalries go, it's hard to get more historic than the California Clasico between the LA Galaxy and San Jose Earthquakes.
Both clubs are MLS originals, though the Earthquakes name went dormant for two seasons when the first franchise moved and became the Houston Dynamo.
And you'd be hard-pressed to find a more decorated fixture in MLS. The Galaxy are the only five-time MLS Cup winners, plus boast a Concacaf Champions Cup and two U.S. Open Cup titles to their name. But San Jose also hoisted MLS Cup twice, once even beating their arch-nemesis to do so.