Barrel Back

How can I go back to a specific date to see what oil (not an etf) was trading at per barrel?
How can I go back to a specific date to see what oil (not an etf) was trading at per barrel? I owned USO and would like to go back to see what actual oil was selling for when I bought it and when I sold it.
I also owned USO for a bit and realized it was an absolutely terrible ETF. Then I found out it bought only the front month contracts. Terrible ETF when there is high contango.
Here is a website that may help you:
http://www.gasbuddy.com/gb_retail_price_chart.aspx
Mark
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