The dramatic collapse in worldwide demand for oil led to an extraordinary development on Monday: U.S. oil prices fell below zero for the first time ever, and kept falling.

The key U.S. oil benchmark, West Texas Intermediate, settled at negative $37.63.

Driven by a trading contract deadline, traders desperately looked for buyers for the barrels of oil they normally hold in their books. But buyers were hard to find — even when the oil was being given away for free.

A key American oil benchmark, West Texas Intermediate, fell by more than 80% on Monday as global oil markets continue to grapple with a pandemic-driven collapse in demand.

At the start of 2020, a barrel of WTI cost around $60.

Shortly after 1:40 p.m. ET on Monday, a barrel was trading for less than $2 — the lowest price the WTI futures market has ever seen.