The U.S. oil sector witnessed a historic day yesterday, as ExxonMobil fell behind its breakaway sister Chevron in market capitalization with $141.6 billion versus $142 billion at NYSE closing, making it America’s most valuable oil company. This is the first time since the breakup of Rockefeller’s Standard Oil in 1911 that Chevron surpassed Exxon in market cap. The reshuffling comes at an unprecedented time for the global oil market, which has been battered by economic lockdowns and an oil price war in the wake of the coronavirus pandemic. But the real story here is not so much one of Chevron’s rise, but rather Exxon’s decline.