The United States Oil Fund (NYSE:USO) just logged the biggest trading day in its 20-year history on Monday, with an eye-popping $16 billion changing hands as retail and institutional traders piled into the oil spike and subsequent reversal.

USO is moving. See the chart and price action here. 

$16 Billion in USO

Bloomberg ETF analyst Eric Balchunas highlighted the move with a chart showing that Monday's tally towers over every prior session in the fund's life, calling it "the peak" but adding that he thinks "we cool off from here." 

Finally tally for USO was $16b of volume. Here's how that looks vs every other day of trading in its 20yr life. My guess is this is the peak, we cool off from here. But what a comeback in relevancy for ...