Which oil field, discovered in 1930, is the largest in the contiguous United States?

The East Texas Oil Field, discovered in 1930, is the largest oil field in the contiguous United States.

The discovery came during the Great Depression, when wildcatter Columbus Marion “Dad” Joiner persisted despite earlier failed drilling attempts. On October 3, 1930, his Daisy Bradford No. 3 well near Henderson, Texas, struck oil at roughly 3,536 feet. Subsequent wells showed that the discovery was part of one enormous connected reservoir.

The field covers about 140,000 acres across five counties, including Gregg, Rusk, Upshur, Smith, and Cherokee. Its relatively shallow depth and high-quality crude triggered a major drilling rush. Kilgore became especially famous: at one point, more than 1,000 wells crowded its downtown area.

Spindletop is another famous Texas discovery, but it dates to 1901 and is not the largest field in the lower 48. Prudhoe Bay is larger than East Texas overall, but it lies in Alaska, outside the contiguous United States. Yates is also a major field, but not the intended answer.